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At least 235 records · Page 13Linked to original sources
PubMed1996

Effects of hyperhydration on total body water, temperature regulation and performance of elite young soccer players in a warm climate.

The purpose of this study was to test the effect of increased fluid intake on temperature regulation and performance in elite soccer players. Eight players of the Puerto Rico National Team were studied under field conditions at a Wet Bulb Globe Temperature (WBGT) heat stress index of 25.3 +/- 0.5 degrees C. They were young (17.0 +/- 0.6 yr) and well aerobically conditioned, as shown by their maximum aerobic power of 69.2 +/- 0.7 ml.kg(-1).min(-1). Players were randomly allocated to a week of voluntary hydration (VH) (fluid intake = 2.7 +/- 0.2.day(-1)) and a week of hyperhydration (HH) (fluid intake = 4.6 +/- 0.2.day(-1)) (p <0.05) prior to a soccer match. Their total body water (TBW) increased in HH compared to VH (p<0.05), despite a significant increase in urine output (p < 0.01). The soccer match was played at 82 +/- 7% (VH) and 83 +/- 6% (HH) of maximum heart rate. Sweat losses and core temperature increases during the match were similar in both hydration conditions. When the environmental conditions were taken into consideration, the increase in core temperature during the match rose, as a function of the heat stress index, only in VH (p < 0.05). Plasma volume was slightly reduced in both hydration conditions (ns). Performance assessment at the end of the soccer match revealed that average time to complete 7 repetitions of a soccer specific test was significantly increased (p < 0.05) after the match in both hydration conditions but showed no difference between them. Peak torque and fatigability of knee flexor and extensor muscle groups at 240 deg.sec(-1), measured on a Cybex 340 dynamometer were similar in both hydration conditions and not affected by the soccer match. The data suggest that additional water intake in these heat-acclimated players increased body water reserves and improved temperature regulation during a soccer match with no significant effect on the decrement in soccer specific performance observed at the end of a soccer match.

Body Temperature Regulation↗
PubMed1984

Regulation of body temperature and nociception induced by non-noxious stress in rat.

The effects of 3 different non-noxious stressors on body temperature (Tb) were investigated in the rat: (1) loose restraint in cylinders, (2) removal of the rats from cylinders, exposure to a novel environment and replacement in cylinders, a stressor called here 'novelty', and (3) gentle holding of the rats by the nape of the neck. Loose restraint and 'novelty' produced hyperthermia. On the contrary, holding induced hypothermia. Hypophysectomy (HX) reduced basal Tb, abolished restraint hyperthermia and reduced both 'novelty' hyperthermia and holding hypothermia. Dexamethasone ( DEXA ) had no effect upon either restraint or novelty hyperthermia but reduced the hypothermia. Naloxone (Nx) produced a slight fall in basal Tb accounting for its reduction of restraint and 'novelty' hyperthermias ; it did not affect holding hypothermia. The inhibitory effects of HX suggest a participation of the pituitary in the hyperthermias ; the neurointermediate lobe would be involved as the hyperthermias were not affected by DEXA , which is known to block the stress-induced release of pituitary secretions from the anterior lobe but not from the neurointermediate lobe. In contrast, substances from the anterior lobe might participate in hypothermia due to holding since it is reduced by HX and DEXA . As to the effects of Nx, endogenous opioids would not be significantly involved in the thermic effects of the stressors used in this study; they might play, if any, only a minor role in the regulation of basal Tb. These results are compared with those previously obtained on nociception using the same non-noxious stressors. It emerges that, depending on the stressor, different types of association between thermoregulation and nociception may occur, i.e. hyperthermia with analgesia, hyperthermia with hyperalgesia and hypothermia with hyperalgesia.

Animals↗
PubMed1974

The significance of deep body temperature in regulating the concentration of thyroxine in the plasma of the pig.

1. The activity of the thyroid gland in the pig has been assessed while thermosensitive regions of the hypothalamus or the spinal cord were cooled.2. If the cervical region of the spinal cord was cooled for 3 hr, by means of a thermode in the epidural space, the concentration of thyroxine in the plasma increased to a maximum within the first hour but fell again to the control level or lower within 2 hr of the onset of cooling.3. When a thermode in the preoptic region of the hypothalamus was cooled to 18 or 25 degrees C for 3 hr, the concentration of thyroxine in the plasma increased within the first hour and then declined again. Cooling the thermode to 10 degrees C led to a sustained increase in thyroxine concentration.4. The increase in the concentration of thyroxine in the plasma, on cooling the hypothalamus, was of a similar magnitude whether the ambient temperature was 25 or 15 degrees C.5. Observations on the disappearance of radioactive thyroxine from the plasma indicated that the distribution or metabolism of thyroxine was altered by the cooling of either the hypothalamus or the spinal cord.6. It was concluded that when the preoptic region of the hypothalamus or the cervical region of the spinal cord was cooled the rise in the concentration of thyroxine in the plasma was due at least in part to a change in the metabolism or distribution of thyroxine within the body and not entirely to the stimulation of the thyroid gland as has previously been suggested.

Animals↗
PubMed2000

Comparative thermoregulation of sympatric endothermic and ectothermic cicadas (Homoptera: Cicadidae: Tibicen winnemanna and Tibicen chloromerus).

Measurements of body temperature in the field demonstrated that endothermic cicadas regulate body temperature by behavioral mechanisms as well as by endogenous heat production. Regression analysis suggests both endothermic and ectothermic species are thermoregulating. Body temperature of endothermically active cicadas without access to exogenous heat is approximately the same as the body temperature of basking cicadas. Tibicen winnemanna (Davis) raises body temperature in the field with the heat produced in flight or through the activation of the flight musculature without the act of flight. T. chloromerus (Walker) uses solar radiation to elevate body temperature to the level necessary for activity. The thermal responses of each species are related to its activity patterns with minimum flight temperature and shade-seeking temperatures significantly lower in the endothermic T. winnemanna. Heat torpor temperature appears to be related to the environment rather than behavior pattern. Endothermy in cicadas may serve to uncouple reproductive behavior from environmental constraints; to circumvent possible thermoregulatory problems; to permit the utilization of habitats unavailable to strictly ectothermic cicadas; to reduce predation; to optimize broadcast coverage and sound transmission; and to decrease possible acoustic interference.

Adaptation, Physiological↗
PubMed1997

Early evening melatonin and S-20098 advance circadian phase and nocturnal regulation of core body temperature.

The phase-shifting capacity and thermoregulatory effects of a single oral administration at 18 h of melatonin (5 mg) or S-20098, a melatonin agonist (5 or 100 mg), was investigated in eight healthy young men in a double-blind placebo crossover design. The unmasking conditions of a shortened constant-routine protocol (mini-CR) were used to collect evening phase markers of physiological parameters. In comparison to placebo, all three drug administrations induced an earlier dim-light melatonin onset (DLMO), an earlier increase in distal skin temperature, and an earlier decrease in core body temperature (CBT), heart rate, and proximal skin temperature. This indicates that administration at 18 h of both melatonin and S-20098 (more pronounced with 100 than 5 mg) induced an earlier regulation of the endogenous circadian nocturnal decline in CBT. On the posttreatment day a second mini-CR revealed persistent significantly phase-advanced circadian rhythms as estimated by DLMO, as well as by the midrange crossing time of CBT and heart rate decline. There were no significant differences between the two doses of S-20098. The data suggest that, in addition to immediate thermoregulatory changes, a phase advance of the circadian system had occurred and that the phase advance could still be measured on the posttreatment day.

Acetamides↗
PubMed1989

Temperature regulation during upper body exercise: able-bodied and spinal cord injured.

This paper will consider human thermoregulatory response differences between upper and lower body exercise. In addition, the thermoregulatory problems of spinal cord injured individuals are examined. For able-bodied individuals, the rise in core temperature is independent of the skeletal muscle mass employed and dependent upon the metabolic rate during exercise. The avenues of heat exchange, however, are different for individuals performing upper body as opposed to lower body exercise. During upper body exercise, there is a greater dry heat loss from the torso; however, no additional heat loss (as compared to lower body exercise) occurs from the exercising arms. If an individual performs upper body exercise in cold water, there will be a greater heat loss and susceptibility to hypothermia than during lower body exercise. A spinal cord injury impairs one's ability to thermoregulate because of: (a) loss of autonomic nervous system control for vasomotor and sudomotor responses in the areas of the insensate skin; (b) a reduced thermoregulatory effector response for a given core temperature; and (c) a loss of skeletal muscle pump activity from the paralyzed limbs. As a result, a spinal cord injured person has a reduced ability to tolerate thermal extremes and to perform aerobic exercise. Surprisingly little research, however, has focused on the ability of the disabled to thermoregulate during exercise. Recent data suggest that rectal temperature measurements may underestimate the thermal burden imposed on wheelchair athletes during competition.

Arm↗
PubMed1988

Age-associated decrease in beta-adrenergic receptors and adenylate cyclase activity in rat brown adipose tissue.

The ability to regulate body temperature diminishes with age. In the rat, nonshivering thermogenesis in brown adipose tissue (BAT) serves as the regulator of body temperature. This process is stimulated by catecholamine activation of adenylate cyclase through the beta-adrenergic receptor. However, beta-adrenergic responsiveness also diminishes with age. To investigate the age-related alterations in beta-adrenergic function in BAT, beta-adrenergic receptor number and cytochrome c oxidase activity were assessed in 3-, 12-, and 24-month-old rats, and adenylate cyclase activity was assessed in 3-, 12-, 18-, and 24-month-old rats. The amount of brown adipose tissue recovered from senescent rats was 30% less than that from either the 3- or 12-month-old rats. There was a corresponding decrease in the total amount of cytochrome c oxidase activity in the 24-month-old rats. In the senescent rats, the density of beta-adrenergic receptors was twofold less than in the 3- and 12-month-old rats. The decrease in density was predominately due to a decrease in the beta 1-adrenergic subtype. Isoproterenol- and NaF-stimulated adenylate cyclase activity were threefold greater and forskolin-stimulated activity was fourfold greater in the 3-month than in the older rats. There was no change in the Kact for isoproterenol with age. These biochemical alterations with age may contribute to the inability of older animals to thermoregulate when exposed to cold.

Adenylyl Cyclases↗
PubMed1998

Effects of medium- and long-chain triglycerides on sleep and thermoregulatory processes in neonates.

Sleep processes and body temperature regulation of neonates are never taken into account in the evaluation of nutrients, although these functions are implicated in the regulation of energy metabolism and are influenced by the nutritional state and its metabolic consequences. Medium-chain triglycerides (MCT) are currently used in paediatric units during the first weeks of because they are considered to be a rapid source of energy, easy to assimilate for growing premature infants, whose digestive function is immature. However, no study has described the thermic effect of these nutrients on body temperature regulation and sleep. The present study aimed at analysing the influence of three feeding formulas with different content of MCT on sleep processes and on thermoregulation of neonates fed until desired intake was reached. Whatever the thermal conditions (thermal equilibrium or cool environment), the MCT-fed groups had higher body temperatures and than groups fed without MCT, for whom total sleep time was reduced at thermal equilibrium. In this group, the large amount of quiet sleep seems to favour a strategy of conserving energy. Higher energy expenditure in MCT-fed groups is not harmful to growth rate since nutritional efficiency is even better reflected by a larger body mass gain. The thermic effect of MCT contributes to lessening the vulnerability of neonates exposed to low incubator temperatures.

Body Mass Index↗
PubMed1992

[Thermal regulation disturbance in severely handicapped patients--the second report].

Thirty-three severely handicapped patients were investigated on body temperature regulation by rectal temperature monitoring and hypophyseal hormonal function. The lowest body temperature in the day in the cases with handicaps of prenatal onset tended to be lower than that of peri or postnatal onset. This finding suggests that different causes make regulation disturbance of body temperature in handicapped children. On the other hand, low urine osmolarity in the morning and irregular menstruation were recorded suggesting hypothalamic dysfunction in poor regulation cases.

Body Temperature Regulation↗
PubMed2006

Effects of the 5-HT7 receptor antagonist SB-269970 on rat hormonal and temperature responses to the 5-HT1A/7 receptor agonist 8-OH-DPAT.

The physiological function of 5-HT(7) receptors is not yet fully determined. This study was designed to characterize the involvement of 5-HT(7) receptor in rat body temperature regulation and in adrenocorticotropic hormone (ACTH) and corticosterone secretion. In the first part of our study, acute administration of SB-269970 (0.1-1 mg/kg, i.p.), a potent and selective 5-HT(7) receptors antagonist, dose-dependently prevented 5-HT(1A/7) receptor agonist 8-OH-DPAT (0.1 mg/kg, s.c.)-induced hypothermia and when the 5-HT(1A) receptor antagonist WAY-100,635 was co-injected with SB-269970, a reduction of the latter hypothermia was obtained in an additive manner. In contrast, 1 mg/kg (i.p.) of SB-269970 failed to prevent 8-OH-DPAT (0.5 mg/kg, s.c.)-induced increase of ACTH and corticosterone plasma levels. In conclusion, the present results unveil an additive effect of both 5-HT(1A) and 5-HT(7) receptors in core body temperature regulation.

8-Hydroxy-2-(di-n-propylamino)tetralin↗