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Biomedical subjects

M Cabanac

Publications and source records attributed to M Cabanac.

At least 73 records · Page 4Linked to original sources
PubMed1989

Cephalic postprandial thermogenesis in human subjects.

To study the role of food palatability on postprandial thermogenesis, a study was designed in which human subjects ingested palatable food while O2 consumption was measured continuously during 30 minutes before and 60 minutes after the meal. In a first experiment (normal feeding), the subjects ate a portion of sugar pie containing 1672 kJ. A rapid increase in O2 consumption was noted which reached a peak value at about 15 minutes from the beginning of the meal. In a second experiment (sham feeding), the subjects were given the same food and they were asked to chew it and to spit it out. During the first 30 minutes following the meal, sham feeding produced a significantly larger increase in O2 consumption than meal feeding, whereas in the second postprandial period the thermogenic effect of food was larger with meal feeding. The integrated elevation of O2 during one hour was the same with meal feeding as with sham feeding. These results show that sensory stimulations without food being absorbed caused an important increase in O2, and confirms in humans the presence of a cephalic postprandial thermogenesis. In the third experiment (blank feeding), the subjects mimicked the muscular activities associated with feeding such as hands, arms, jaw and throat movements. Blank feeding produced a small and transient increase in O2 consumption. An elevation of plasma norepinephrine was observed during the cephalic phase and this effect was significantly larger with sham than with meal feeding. Subjective ratings for palatability, hunger reduction and degree of fullness were higher with meal than with sham feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Effects of dexfenfluramine on the feeding behavior of rats foraging in the cold for palatable bait.

An alimentary/thermic conflict of motivation was used to explore the effects of very low doses of dexfenfluramine (dFF), an anorectic serotoninergic agonist, on the parameters of food motivation, drive and incentive (or palatability). Six rats trained to feed 2 hr/day, were given the possibility to feed on chow in a shelter (25 degrees C), and to get a snack of shortcake, a highly palatable bait, from a feeder placed 16 m away in a very cold environment (-15 degrees C). dFF at 0.6 or 1.25 mg/kg decreased neither the chow intake in the shelter, nor the mean duration of the snacks in the cold, which is the parameter believed to be the best indicator of incentive. In contrast, dFF reduced the number of trips to the bait in the cold as well as the total mass of palatable bait ingested and the mean amount ingested by snack. Such an effect was no longer observed after a food restriction had reduced the body weight of the rats to 90% of its initial value. It is concluded that, even at doses too small to reduce the consumption of basic food, dFF decreases the drive to get palatable food.

Animals↗
PubMed1989

Lack of caloric regulation in rats during short-term feeding.

Rats were trained to feed 2 h daily. Each rat was presented during three 10-day-long alimentary periods with each of the following diets: control (C), low calorie (L), and high calorie (H). The food was placed at an ambient temperature of -15 degrees C at 16 m from a warm refuge. It was found that the rats ingested similar amounts of food, regardless of energy density of the diet, and therefore did not compensate for variations in the caloric density of a diet. This was despite the recognition of a novel diet on the first day of its presentation as manifested by a change in rats' meal pattern. L diet was eaten slowly, suggesting that it was less palatable than the C or H diets. The results suggest that the rat placed in a closed economy with only short-term access to food imposed by a hostile environment does not adjust its food intake in accordance with energy value of the food. Its momentary food intake appears to be controlled by the gustatory properties of the food.

Animals↗
PubMed1989

Rats eating and hoarding as a function of body weight and cost of foraging.

Rats were trained to forage 2 h daily in a zigzag alley at -15 degrees C. On experimental days food was placed in large amounts at a 1-, 4-, or 16-m distance from a warm shelter. The mass of food ingested and hoarded in the shelter by the rats was then recorded. The rats' body weights were depressed progressively by spacing the sessions with access to food, and then the animals were allowed to recover their initial body weight. The results showed that 2-h food intake was constant and did not vary as a function of body weight loss or the distance to reach the food (cost). On the other hand, the mass of food hoarded was a linear increasing function of body weight loss below the hypothetical set point for body weight and a decreasing linear function of the distance to the food. The linear regression of the mass of food hoarded on body weight with a negative slope (b) adequately depicted the rat's hoarding behavior: mass hoarded = a + b (body wt). The slope of this function decreased with increasing cost of food procurement. It is concluded that 1) the main response of the rat to starvation is food hoarding rather than ingestion and 2) the estimation of the body weight set point from hoarding is not affected by the costs of food procurement.

Animals↗
PubMed1989

[Maximization of pleasure, the answer to a conflict of motivations].

An experiment has been set up to explore the hypothesis according to which behaviour is determined by the trend to maximize pleasure. Twelve subjects were placed individually in a situation of conflict where the pleasure of playing a videogame clashed with the increasing discomfort of a cold environment. The time lapse tolerated could be predicted from the algebraic sum of the rating of displeasure aroused by the cold environment and the rating of pleasure aroused by the videogame, obtained in other sessions. This result supports the working hypothesis and allows to conclude that pleasure is the common currency of tradeoffs among various motivations.

Cold Temperature↗
PubMed1988

Precedence of head homoeothermia over trunk homoeothermia in dehydrated men.

Three male humans were subjected repeatedly to 20 min exercise on a bicycle ergometer: twice when hydrated normally and twice when dehydrated. Tympanic (Tty) and oesophageal (Tes) temperatures were recorded and sweat rates on forehead and back were measured. Dehydration did not change the forehead sweat rate, but on the back it reduced significantly, resulting in an increase of Tes. However, Tty was decreased by dehydration. 20 min after the end of exercise subjects were allowed to drink water in order to trigger the potohidrotic response. A potohidrotic response was noted on the back of dehydrated subjects only. It is concluded that dehydration results in active inhibition of sweating on the body but not on the forehead, where evaporation is needed for selective cooling of the brain.

Body Temperature↗
PubMed1988

Beards, baldness, and sweat secretion.

The hypothesis according to which male common baldness has developed in the human species as a compensation for the growth of a beard in order to achieve heat loss has been tested. In 100 clean-shaven men direct measurement of the area of glabrous skin on the forehead and calvaria was found to be proportional to that of the hairy skin on the lips, cheeks, chin and neck. During light hyperthermia the evaporation rate on the bald scalp was 2 to 3 times higher than on the hairy scalp. Conversely the evaporation rate was practically equal on the foreheads and chins of women and unbearded young men, while in adult clean-shaven bearded men it was 40% less on the chin than the forehead. These results support the hypothesis that male baldness is a thermoregulatory compensation for the growth of a beard in adults.

Adolescent↗
PubMed1988

Local thermal sensation and finger vasoconstriction in the locally heated hand.

The effects of local heating on finger blood flow (BF) and local thermal sensation (Sensw) were studied. Finger BFs in both hands were measured simultaneously; one hand was immersed in water the temperature (Tw) of which was raised from 35 degrees C to 43 degrees C by steps of 2 degrees C every 10 min, while the other hand was kept at Tw 35 degrees C. Finger BF in the locally heated hand decreased at Tw 37 to 41 degrees C, while finger BF in the control hand did not alter. Sensw in the heated hand showed a dynamic response, initially increasing concomitantly with an increase in Tw, then gradually returning and adapting to a new level of Sensw. The dynamic response of Sensw was not perceived during mental calculation even when Tw was raised to 40 degrees C, and the reduction in finger blood flow was not observed. These results suggest that finger vasoconstriction caused by local heating closely relates to the dynamic response characteristic of local thermal sensation at Tw above core temperature, and that the perception of local thermal sensation in the central nervous system is involved in the mechanism of this vasoconstrictor response.

Adult↗
PubMed1988

[Regulation of body weight and food palatability].

It is as though the body weight, or a variable correlated closely with body weight, was submitted to regulation. This regulation is analyzed from known human studies. This short bibliography study reviews interrelations between palatability of food stuffs and ponderostat. Findings show that palatability elevates ingestion rate, metabolic output rate and ponderostat set point. Reciprocally, ingestion and the set point modulate food palatability.

Basal Metabolism↗
PubMed1987

Tympanic temperatures during hemiface cooling.

In adult men the left half of the head was covered with thick heat insulation, and the right hemiface was cooled by spraying a mist of water, and vigorous fanning. The subjects were immersed up to the waist in warm water (42 degrees) to achieve hyperthermia. In control sessions the subjects were rendered slightly hypothermic by preliminary exposure to cold. Under the hypothermic condition during right skin cooling, the right Tty remained low as compared with oesophageal temperature, while the left Tty was raised. Under the hyperthermic condition right hemiface cooling maintained not only the right Tty lower than oesophageal but also, to a lesser extent the left Tty, while the skin on the left side was close to core temperature. This latter result cannot be explained by conductive cooling from the skin to the tympanic membrane and implies a vascular cooling of the left Tty originating from the other side of the head. It is concluded that selective cooling of the brain takes place during hyperthermia. The main mechanism is forced vascular convection, but conductive cooling also occurs.

Adult↗
PubMed1987

Enhanced brain protection during passive hyperthermia in humans.

Selective brain cooling during hyperthermia by emissary venous pathways from the skin of the head to the brain has been reported both in animals and humans. Heat protection of the brain extends tolerance to high deep body temperature in animals, and may be enhanced in humans if the head is cooled. In order to quantify to what extent brain protection could be obtained by face fanning, 9 non-anesthetized human volunteers were placed in ambient conditions as close as possible to those of passive therapeutic hyperthermia. Face-fanning maintained tympanic temperature 0.57 degrees C lower than esophageal temperature, and improved comfort. External head cooling techniques enhancing physiological brain cooling can therefore be useful for the protection of the human brain during heat stress or passive therapeutic hyperthermia.

Adult↗
PubMed1987

Influence of noise on gustatory affective ratings and preference for sweet or salt.

Ten adult men were exposed to four different conditions of noise--low noise (70 dB), loud noise (90 dB), loud music (90 dB) and a silence control--while they tasted sweet or salty solutions. In the first experiment, they rated the pleasure/displeasure aroused by ten gustatory stimuli (five sucrose and five sodium chloride from 0.15 to 2.35 M/l). The median affective rating for sucrose was significantly higher in loud noise and with loud music. No change was observed for salt. In the second experiment, the subjects were invited to mix solutions in order to obtain the most pleasant concentration of sucrose or sodium chloride. Subjects' preferred concentrations of sucrose or sodium chloride did not vary with auditory conditions.

Adult↗
PubMed1987

Fever in snails, reflection on a negative result.

1. Groups of aquatic snails (Limnaea auricularia) were placed in a temperature gradient and their thermopreferendum measured. 2. Injected with various amounts of killed Escherichia coli, bacterial endotoxin, human interleukin, and prostaglandin E1, E2 and F2 alpha, they did not develop a fever. 3. High doses of prostaglandins were toxic. 4. These results suggest that fever appeared in the course of evolution after the emergence of molluscs and before that of arthropods.

Animals↗
PubMed1987

Pleasure and preference in a two-dimensional sensory space.

A matrix of 25 gustatory stimuli combined five sucrose concentrations (0.15 to 2.35 mole/l) with five temperatures (10 to 50 degrees C) or sournesses (pH 1.8 to 5.7). On four different days at the same time of day ten healthy young men served as subjects. Sweet pleasure/displeasure vs. temperature pleasure/displeasure was studied in four subjects and sweet pleasure/displeasure vs. sourness pleasure/displeasure in six subjects. Throughout the first session the 25 stimuli were presented for 5 s each and the subject gave a magnitude estimate of his pleasure or displeasure in response to one dimension of the matrix (e.g. sweetness) regardless of the other. Similarly, throughout the second session, the same stimuli were presented and the subject rated his pleasure or displeasure in response to the second dimension of the matrix (e.g. sourness or temperature) regardless of the first. For the third session however, the subject himself was invited to mix samples, this to allow a behavioural choice in one dimension of the matrix the other being imposed (e.g. he could mix sucrose and water ad libitum for five imposed temperatures). For the last session the subject could adjust the previously imposed dimension, the other previously adjustable dimension being now imposed (e.g. he could modify temperature for five imposed sucrose concentrations). The results of the first two sessions showed that pleasure/displeasure resulted from a two-dimensional combination of the taste modalities offered. The results of the last two sessions showed that the subjects tended to maximize their sensory pleasure. The operant choices coincided with the ratings obtained in the first two sessions. Whether a dimension of the matrix was imposed or operantly adjustable made no difference on the results; the subjects tended to maximize sensory pleasure in the imposed dimension as well as in the adjustable dimension. The subjects therefore maximized their pleasure in the two-dimensional space offered.

Adolescent↗
PubMed1987

The effect of face fanning during recovery from exercise hyperthermia.

Hyperthermia was induced in nine subjects on two separate occasions by a progressive treadmill run, which resulted in an average esophageal temperature (Tes) of 39.77 +/- 0.07 degree C after 30-57 min. Fanning the face during exercise to simulate conditions during running (wind at 3.75 m X s-1) maintained a tympanic temperature (Tty) that was lower than Tes; the difference was 1.5 degrees C at the end of exercise. In one session, face fanning was interrupted at the end of running, whereas in the other it was maintained for 15 min after exercise stopped. Face fanning had no significant influence on the fall of Tes during recovery, but it markedly influenced the course of Tty during this period. When face fanning was stopped at the end of the run, Tty rose by nearly 0.5 degree C, peaked after 4.5 min, and thereafter decreased slowly to a value close to Tes. In contrast, when face fanning was maintained throughout the recovery period, Tty rose only slightly (0.1 degree C) and remained significantly lower than Tes at all times. The results suggest that following hyperthermic exercise, face fanning could be helpful in preventing acute cerebral hyperthermia.

Adult↗
PubMed1987

The effect of local heating on blood flow in the finger and the forearm skin.

Blood flow of the finger and the forearm were measured in five male subjects by venous occlusion plethysmography using mercury-in-Silastic strain gauges in either a cool-dry (COOL: 25 degrees C, 40% relative humidity), a hot-dry (WARM: 35 degrees C, 40% relative humidity), or a hot-wet (HOT: 35 degrees C, 80% relative humidity) environment. One hand or forearm was immersed in a water bath, the temperature (Tw) of which was raised every 10 min by steps of 2 degrees C until it reached 41 degrees or 43 degrees C. While the other hand or forearm was kept immersed in a water bath (Tw, 35 degrees C), blood flow in the heated side (BFw) was compared with the corresponding blood flow in the control side (BFc). Under WARM or HOT conditions, finger BFw was significantly lower than finger BFc at a Tw of 39-41 degrees C in the majority of subjects. When Tw was raised to 43 degrees C, however, finger BFw became higher than BFc in nearly half of the subjects. In the COOL state, finger BFw did not decrease but increased steadily when Tw increased from 37 degrees to 43 degrees C. In the forearm, BFw increased steadily with increasing Tw even in WARM-HOT environments. No such heat-induced vasoconstriction was observed in the forearm. From these results we conclude that in hyperthermic subjects, the rise in local temperature to above core temperature produces vasoconstriction in the fingers, an area where no thermal sweating takes place.

Adult↗