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PubMed2001

Postpartum chills phenomenon: is it a feto-maternal transfusion reaction?

OBJECTIVE: To examine the theory that the postpartum shivering phenomenon is related to feto-maternal bleed during the third stage of labor. METHODS: One hundred laboring low-risk women who had a normal vaginal delivery were observed for the presence of postpartum chills. The duration of the first and second stages of labor changes in body temperature, maternal and fetal blood types and the use of epidural anesthesia were recorded. Following the delivery maternal blood was examined for the presence of fetal red blood cells using the Kleihauer-Betke stain. RESULTS: Complete data was available in 97 patients. Post-partum chills occurred in 31 of them (32%). Women with and without chills were similar in their maternal and gestational age, the use of epidural anesthesia, and length of second stage of labor. Women with chills delivered smaller babies but the difference did not reach significance. Maternal-fetal blood group incompatibility was significantly more common among shivering than non-shivering women (48% vs. 20% respectively, p=0.006). Kleihauer-Betke test was positive in 11 women. The only two women in this group who experienced chills had maternal-fetal blood group incompatibility. CONCLUSION: Post-partum chills are a common phenomenon. It may be the clinical presentation of feto-maternal transfusion reaction. The small number of positive Kleihauer-Betke tests may reflect its low sensitivity in the detection of small feto-maternal bleeds.

ABO Blood-Group System↗
PubMed1976

Peripheral heat as a reward for heart rate response in the curarized rat.

It is generally assumed that the mechanical perception of shivering is necessary for the perception of cold discomfort. Shivering of rats in a cool environment was eliminated by curarization. The rats were kept alive by artificial respiration. Heart rate was proportional to rectal temperature in a group of controls. One group of rats was conditioned to increase heart rate to trigger an infrared lamp; another group was conditioned to decrease heart rate to obtain heat. When compared with the results of the control group without infrared heat reward, the results obtained from the two heart-rate-modifying groups show that shivering is not a necessary signal to determine thermoregulatory behavior in rats and, presumably, cold discomfort in man.

Animals↗
PubMed1996

alpha-Adrenoceptor mechanisms of thermoregulation during cold challenge in humans.

1. Previous studies on the thermoregulatory effects of alpha-adrenoceptor antagonists have been performed primarily in animals and the findings have been inconsistent. There is evidence for thermoregulatory impairment by alpha-adrenergic antagonists in humans not exposed to cold, but the effects of alpha-adrenergic blockade during cold challenge have not been investigated. 2. Fourteen healthy human volunteers (seven elderly, aged 55-68 years and seven young, aged 19-27 years) were studied on three separate days and received three randomly assigned treatments; (i) control (no drug), (ii) low-dose phentolamine and (iii) high-dose phentolamine. On each day cold intravenous saline (4 degrees C) was given until both vasoconstriction and shivering were triggered or a maximum fluid volume (40 ml/kg) was delivered. Core temperature, peripheral vasoconstriction and metabolic heat production were measured. 3. The alpha-adrenoceptor antagonist caused a dose-dependent inhibition of vasoconstriction in the elderly but did not impair vasoconstriction in the young subjects at the doses that were given. Shivering and metabolic heat production were unaffected by alpha-adrenergic blockade in the elderly or in the young. 4. These findings illustrate the selective inhibition of vasoconstriction (but not shivering) by alpha-adrenoceptor antagonism in elderly individuals. Compared with the young, the elderly are more sensitive to the effects of alpha-antagonists, perhaps due to downregulation of the alpha-adrenoceptor. These findings lead us to conclude that thermoregulatory vasoconstriction is alpha-adrenergically mediated, and this response is attenuated by alpha-adrenoceptor blockade in elderly humans.

Adrenergic alpha-Antagonists↗
PubMed1998

Poikilothermia syndrome.

Poikilothermia syndrome is a rare cause of intrinsic thermoregulatory failure. Patients with this syndrome regulate body temperature poorly, if at all. Recently, a patient was referred to us who had clinical evidence of poikilothermia syndrome, as well as long-standing multiple sclerosis. Computerized tomography and magnetic resonance scanning failed to identify a hypothalamic lesion. The patient was gradually warmed to sweating, and then cooled to vasoconstriction and shivering. The core-temperature thresholds triggering each defence were calculated, after compensating for the changes in skin temperature. The calculated sweating threshold was 38.3 degrees C (normal: 37.0 +/- 0.3 degrees C). The vasoconstriction threshold was 34.4 degrees C (normal: 36.4 +/- 0.3 degrees C). The sweating-to-vasoconstriction interthreshold range was thus approximately 4 degrees C, which is between 10 and 20 times the normal value. The shivering threshold was 31.8 degrees C (normal: 35.6 +/- 0.3 degrees C). The vasoconstriction-to-shivering range was thus approximately 2.5 degrees C which is more than twice the normal value. The pattern of thermoregulatory failure in this patient resembled that resulting from general anaesthesia.

Body Temperature↗
PubMed1991

Dissociation of thermoregulation in cats with cytotoxic pontine lesions.

Neurons of the pontine tegmentum of the cat were lesioned by microinjection of ibotenic acid into the brainstem. The threshold ambient temperatures for heat-gain (shivering) and for heat-loss (panting) responses, together with brain and skin temperatures, were measured in intact animals and after the neurotoxic lesioning. After the lesioning the shivering threshold was altered but the panting threshold did not change. The results indicate that certain neurons involved in the shivering response reside in the pontine tegmentum. Neurons involved in the panting response, however, may lie outside the lesioned areas.

Animals↗
PubMed1981

Neurologic changes during awakening from anesthesia.

Transient hyperreflexia, the Babinski reflex, and other transient neurologic signs may follow anesthesia in healthy persons. The authors describe the appearance and durations of these signs and relate them to anesthetic agent, time following cessation of anesthesia, and state of arousal. Twenty-nine neurologically normal male patients undergoing superficial operations were anesthetized with halothane-nitrous oxide, enflurane-nitrous oxide, or nitrous oxide-narcotic. During awakening, patients experienced transient hyperreflexia and shivering following all anesthetic techniques. Quadriceps hyperreflexia occurred in three of eight patients after halothane-N2O, seven of 12 patients after enflurane-N2O, and no patient after n2O-narcotic anesthesia. Sustained ankle clonus and upgoing plantar responses were observed most frequently following enflurane-N2O (50 percent of patients). Following halothane-N2O, ankle clonus was observed in 12.5 per cent of patients and upgoing plantar responses in 25 per cent of patients. Neither sign occurred after N2O-narcotic anesthesia. Shivering, too, was observed most frequently following enflurane anesthesia (66 per cent of patients). There were equal reductions of body temperature in shivering and nonshivering patients. In every patient, regardless of the anesthetic used, the lash reflex and the pupillary response to light returned to normal with the return of consciousness as measured by the response to verbal commands. It is concluded that the neurologic profile during awakening from general anesthesia is most abnormal following enflurane-N2O, compared with halothane-N2O and N2O-narcotic anesthesia. Abnormalities are found most frequently when patients are poorly responsive to verbal commands. Although their incidence diminishes with time, abnormal responses to neurologic examination may persist for 40 min or more after cessation of anesthesia.

Adult↗
PubMed1992

The effect of 30% nitrous oxide on thermoregulatory responses in humans during hypothermia.

Clinical studies have reported that body core temperature decreases during prolonged surgery and anesthesia. Although this finding has been attributed primarily to increased heat loss resulting from exposure of body cavities and infusion of cold solutions, it is generally recognized that anesthesia interferes with the thermoregulatory system. The present study examined the effects of mild narcosis induced by 30% N2O on shivering thermogenesis and cutaneous thermoregulatory vasoconstriction in humans, during exposure in a much more intense peripheral thermal stimulus than the ones often used in clinical studies. Nine male subjects were immersed in 15 degrees C water on two separate occasions. During one occasion subjects inspired air (control condition), and during the other occasion the inspired gas mixture contained 20% O2, 30% N2O, and 50% N2 (N2O condition). On both occasions, subjects were immersed to the neck for 60 min, or until their core temperature decreased by 2 degrees C from the preimmersion value. Following the cooling phase, subjects rewarmed via endogenous thermogenesis while lying in a well-insulated bed for 48 min. In the N2O condition, subjects continued to inspire the anesthetic gas mixture during the 48-min period of recovery. O2 uptake (VO2), esophageal temperature (Tes), mean skin temperature (Tsk), mean heat flux (Q) and forearm-fingertip temperature gradient (Tsk-gr) were recorded at 1-min intervals. Tsk and Q in both conditions stabilized within 10 and 25 min of immersion, respectively, and were not significantly different between the two conditions. The cooling rate of Tes was greater during the N2O than the control condition. VO2 increased during the immersion in both conditions and was greater in the control than in the N2O condition. In both conditions, VO2 increased linearly with decreasing Tes, but at any given Tes, VO2 was higher in the control than in the N2O condition. No significant difference was observed in cutaneous thermoregulatory vasoconstriction between the two experimental conditions, as indicated by the Tsk-gr values. The estimated Tes threshold for shivering (estimated from the O2 consumption vs. delta Tes regression) was reduced by 0.95 +/- 0.26 (SE) degrees C during the immersion phase and by 0.39 +/- 0.05 (SE) degrees C during the rewarming phase in the N2O condition compared to the control conditions. Although the thermosensitivity (gain) of shivering appeared preserved during the immersion phase, it was reduced during the N2O rewarming phase.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Inhalation↗
PubMed1997

Influence of thermoregulatory vasomotion and ambient temperature variation on the accuracy of core-temperature estimates by cutaneous liquid-crystal thermometers.

BACKGROUND: Recently, liquid crystal skin-surface thermometers have become popular for intraoperative temperature monitoring. Three situations during which cutaneous liquid-crystal thermometry may poorly estimate core temperature were monitored: (1) anesthetic induction with consequent core-to-peripheral redistribution of body heat, (2) thermoregulatory vasomotion associated with sweating (precapillary dilation) and shivering (minimal capillary flow), and (3) ambient temperature variation over the clinical range from 18-26 degrees C. METHODS: The core-to-forehead and core-to-neck temperature difference was measured using liquid-crystal thermometers having an approximately 2 degrees C offset. Differences exceeding 0.5 degree C (a 1 degree C) temperature range) were a priori deemed potentially clinically important. Seven volunteers participated in each protocol. First, core-to-peripheral redistribution of body heat was produced by inducing propofol/desflurane anesthesia; anesthesia was then maintained for 1 h with desflurane. Second, vasodilation was produced by warming unanesthetized volunteers sufficiently to produce sweating; intense vasoconstriction was similarly produced by cooling the volunteers sufficiently to produce shivering. Third, a canopy was positioned to enclose the head, neck, and upper chest of unanesthetized volunteers. Air within the canopy was randomly set to 18, 20, 22, 24, and 26 degrees C. RESULTS: Redistribution of body heat accompanying induction of anesthesia had little effect on the core-to-forehead skin temperature difference. However, the core-to-neck skin temperature gradient decreased approximately 0.6 degree C in the hour after induction of anesthesia. Vasomotion associated with shivering and mild sweating altered the core-to-skin temperature difference only a few tenths of a degree centigrade. The absolute value of the core-to-forehead temperature difference exceeded 0.5 degree C during approximately 35% of the measurements, but the difference rarely exceeded 1 degree C. The core-to-neck temperature difference typically exceeded 0.5 degree C and frequently exceeded 1 degree C. Each 1 degree C increase in ambient temperature decreased the core-to-fore-head and core-to-neck skin temperature differences by less than 0.2 degree C. CONCLUSIONS: Forehead skin temperatures were better than neck skin temperature at estimating core temperature. Core-to-neck temperature differences frequently exceeded 1 degree C (a 2 degrees C range), whereas two thirds of the core-to-forehead differences were within 0.5 degree C. The core-to-skin temperature differences were, however, only slightly altered by inducing anesthesia, vasomotor action, and typical intraoperative changes in ambient temperature.

Adult↗
PubMed1990

A comparison of three methods of managing fever in the neurologic patient.

Patients with neurological dysfunction can suffer fevers due to irritation of, or damage to the temperature-regulating center in the brain, or a combination of both. Although hypothermic therapy is a critical treatment nurses often perform, the most effective cooling method has not been studied in the neurological patient. The purpose of this quasi-experimental study was to compare the effectiveness of three methods of fever reduction, and the effect of each on patient shivering. Twenty-one adult febrile neurological patients were randomly placed in one of three temperature reduction groups. One of the temperature reduction protocols was initiated when a subject first became febrile. Rectal temperatures were taken every 15 minutes using an IVAC Temp-Plus thermometer until the subject's temperature returned to 100 degrees F. Subjects were observed for shivering throughout the procedures. The mean time necessary for the subject's temperature to return to 100 degrees F was calculated. A one-way analysis of variance of the time required to reach 100 degrees F was done to determine if a significant difference existed in rate of temperature reduction among the groups. The analysis revealed no statistically significant difference among the three methods, but a chi-square analysis indicated a significant relationship between shivering and the use of a hypothermia blanket.

Acetaminophen↗
PubMed1981

Human body temperature and controlled cold exposure during moderate and severe experimental alcohol-intoxication.

In an attempt to obtain more conclusive data, especially concerning the condition in many cases of very high alcohol concentration, two groups of healthy volunteers were exposed to controlled cold surroundings in a climate chamber after i.v. infusion of 96% ethyl alcohol, 1-2 1/2 ml per kg bodyweight, supplemented with alcohol perorally; the maximum blood alcohol concentration measured was 57 mmol/l, corresponding to 2.62%. One group was not habituated to drinking; the other group was habituated to heavy drinking, but functioned well socially. During the stay in a neutral environment, the alcohol infusion caused a rapid elevation of skin temperature with a short, but significant delay in temperature elevation in the alcohol-habituated group. After controlled exposure to cold, a rapid fall in surface temperature back to pre-alcoholic infusion values was seen in both groups. During cold exposure, core temperature remained unchanged in both groups. No changes in plasma catecholamines were found. A 12-18% increase in metabolic rate was seen in both groups during cold exposure, probably as an expression of the specific dynamic effect of alcohol. That the observed vasoconstriction was sufficient to prevent an undue fall in core temperature is further supported by the fact that neither shivering, nor non-shivering thermogenesis was activated, as no visible shivering occurred and no rise in plasma catecholamines was seen.

Alcoholic Intoxication↗
PubMed1972

Changes in body temperature produced by cholinomimetic substances injected into the cerebral ventricles of unanaesthetized cats.

1. The effects on body temperature of a number of substances injected into a lateral cerebral ventricle were examined in the unanaesthetized cat.2. Nicotine (50 and 100 mug) caused a fall in body temperature ranging from 0.95-2.1 degrees C associated with skin vasodilatation, tachypnoea and panting. These responses were prevented by the intraventricular injection of hexamethonium or mecamylamine, but not of atropine or phentolamine.3. Carbachol (5 mug) caused a rise in temperature associated with skin vasoconstriction, piloerection and severe shivering. These effects were prevented by the intraventricular injection of atropine, but not of hexamethonium or mecamylamine.4. An acetylcholine/eserine mixture (10 mug of each) had no reproducible effect on body temperature. Because of the variability in the response, interaction studies with antagonist drugs were not performed.5. Hexamethonium (100 mug) or mecamylamine (100 mug) caused a prolonged rise in temperature, together with skin vasoconstriction, piloerection and intense shivering. Atropine (200 mug) was without effect on body temperature.6. Noradrenaline (100 mug) caused a fall in temperature with skin vasodilatation. The fall was converted to a rise with skin vasoconstriction, piloerection and vigorous shivering following an intraventricular injection of phentolamine (100 mug).7. These observations suggest the existence of cholinergic heat loss and heat gain mechanisms in the hypothalamic thermoregulatory pathways of the cat and the interaction studies with hexamethonium, mecamylamine and atropine, support the involvement of ;nicotinic' and ;muscarinic' receptors within the cholinergic thermoregulatory system.

Acetylcholine↗
PubMed1971

Changes in body temperature of the unanaesthetized monkey produced by sodium and calcium ions perfused through the cerebral ventricles.

1. In the unanaesthetized Rhesus monkey, solutions containing sodium, calcium, potassium or magnesium in excess of the normal concentration of extracellular fluid were perfused from a lateral to the fourth ventricle through chronically implanted cannulae.2. Sodium (11.0-88.0 mM in excess of the physiological concentration) perfused through the ventricles, caused an immediate rise in body temperature which was accompanied by vasoconstriction, piloerection and shivering. The latency of the hyperthermia was related directly to the rate of perfusion and the concentration of sodium, whereas the magnitude of the response depended upon the concentration only. When the perfusion was terminated, shivering ceased and the temperature of the monkey returned to the base line level.3. When calcium ions were perfused in concentrations 2.5-47.9 mM in excess of that of extracellular fluid, a fall in the temperature of the animal occurred. The magnitude of the decreases depended upon the concentration of calcium in the perfusion fluid. Vasodilatation, sedation and a reduction in withdrawal reflexes accompanied the calcium-induced hypothermia. After the perfusion ended, the temperature continued to fall until the monkey began to shiver and vasoconstriction was observed in many skin areas.4. The perfusion through the cerebral ventricles with modified Krebs solution alone or with the Krebs solution which contained potassium or magnesium ions in concentrations five to ten times normal had virtually no effect on the temperature of the monkey.5. Since the temperature of the monkey was unchanged as long as the physiological ratio of sodium to calcium in the perfusion fluid remained constant, we conclude that the balance between these two essential cations within the brain stem could determine the neural mechanism whereby the set-point for body temperature of the primate is established.

Animals↗
PubMed1972

Localization of intra-abdominal thermoreceptors in the ewe.

1. In neutral environmental temperatures, shivering was induced in sheep by intra-ruminal cooling. Shivering was then depressed for a period by intra-abdominal heating. Intra-abdominal heating without ruminal cooling induced panting and a reduction of caval temperatures. Posterior caval temperatures were found to be inappropriate to the responses observed.2. Intra-abdominal heating of sheep in cold and warm environments depressed shivering and augmented panting respectively. Unilateral splanchnotomy abolished these responses on the ipsilateral side.3. The results are interpreted to indicate that the thermoreceptors stimulated lie within the walls of the rumen and intestine, and possibly the mesenteric veins.4. The splanchnic nerves are indicated as the afferent pathway for these receptors, and differential splanchnic innervation of the gut is suggested to explain unilateral abolition of the response to warming.

Abdomen↗
PubMed1974

Thermoregulation in endothermic insects.

On the basis of body weight, most flying insects have higher rates of metabolism, and hence heat production, than other animals. However, rapid rates of cooling because of small body size in most cases precludes appreciable endothermy. The body temperature of small flies in flight is probably close to ambient temperature, and that of flying butterflies and locusts is 5 degrees to 10 degrees C above ambient temperature. Many moths and bumblebees are insulated with scales and hair, and their metabolism during flight can cause the temperature of the flight muscles to increase 20 degrees to 30 degrees C above ambient temperature. Curiously, those insects which (because of size, insulation) retain the most heat in the thorax during flight, also require the highest muscle temperature in order to maintain sufficient power output to continue flight. The minimum muscle temperature for flight varies widely between different species, while the maximum temperature varies over the relatively narrow range of 40 degrees to 45 degrees C. As a consequence, those insects that necessarily generate high muscle temperatures during flight must maintain their thoracic temperature within a relatively narrow range during flight. Active heat loss from the thorax to the abdomen prevents overheating of the flight motor and allows some large moths to be active over a wide range of ambient temperatures. Bumblebees similarly transfer heat from the flight musculature into the abdomen while incubating their brood by abdominal contact. Many of the larger insects would remain grounded if they did not actively increase the temperature of their flight muscles prior to flight. Male tettigoniid grasshoppers elevate their thoracic temperature prior to singing. In addition, some of the social Hymenoptera activate the "flight" muscles specifically to produce heat not only prior to flight but also during nest temperature regulation. During this "shivering" the "flight" muscles are often activated in patterns different from those during flight. The muscles contract primarily against each other rather than on the wings. However, the rate of heat production during shivering and flight is primarily a function of the action potential frequency rather than of the patterns of activation. Thermoregulation is a key factor in the energetics of foraging of some of the flower-visiting insects. The higher their muscle temperature the more flowers they can visit per unit time. When food supplies are ample, bees may invest relatively large amounts of energy for thermoregulation. While shivering to maintain high body temperatures during the short intervals they are perched on flowers (as well as while in the nest), bumblebees often expend energy at rates similar to the rates of energy expenditure in flight. Unlike vertebrates, which usually regulate their body temperature at specific set points, the body temperature of insects is labile. It often appears to be maintained near the lower temperature at which the muscles are able to perform the function at hand. The insects' thermal adaptations may not differ as much from those of vertebrates as previously supposed when size, anatomy, and energy requirements are taken into account.

Animals↗
PubMed1998

Winter mortality and cold stress in Yekaterinburg, Russia: interview survey.

OBJECTIVES: To evaluate how mortality and protective measures against exposure to cold change as temperatures fall between October and March in a region of Russia with a mean winter temperature below -6 degrees C. DESIGN: Interview to assess factors associated with cold stress both indoors and outdoors, to measure temperatures in living room, and to survey unheated rooms. SETTING: Sverdlovsk Oblast (district), Yekaterinburg, Russia. SUBJECTS: Residents aged 50-59 and 65-74 living within approximately 140 km of Yekaterinburg in Sverdlovsk Oblast. Survey of sample of 1000 residents equally distributed by sex and age groups. MAIN OUTCOME MEASURES: Regression analysis was used to relate data on indoor heating and temperatures, the amount of clothing worn, the amount of physical activity, and shivering while outside, to outdoor temperature; results were compared with mortality patterns for ischaemic heart disease, cerebrovascular disease, respiratory disease, and mortality from all causes. RESULTS: As mean daily temperatures fell to 0 degree C the amount of clothing worn outdoors increased, physical activity while outdoors became more continuous, and only 11 (6.6%) of the 167 people surveyed who went outdoors at temperatures above 0 degree C reported shivering. The mean temperature in living rooms in the evening remained above 21.9 degrees C. Mortality from ischaemic heart disease, cerebrovascular disease, respiratory disease, and all causes did not change. As the temperature fell below 0 degree C the number of items of clothing worn plateaued at 16.0 and the number of layers at 3.7. With regression analysis, shivering outdoors was found to increase progressively to 34.6% (P < 0.001) of excursions at -25 degrees C, and mortality (after declining slightly) rose progressively (all cause mortality rose by 1.15% for each 1 degree C drop in temperature from 0 degree C to -29.6 degrees C, 95% confidence interval 0.97% to 1.32%). 94.2% of bedrooms were directly heated, and evening temperatures in the living room averaged 19.8 degrees C even when outside temperatures reached -25 degrees C. CONCLUSIONS: Outdoor cold stress and mortality in Yekaterinburg increased only when the mean daily temperature dropped below 0 degree C. At temperatures down to 0 degree C cold stress and excess mortality were prevented by increasing the number of items of clothing worn and the amount of physical activity outdoors in combination with maintaining warmth in houses.

Activities of Daily Living↗
PubMed1973

Intermittent hypothermia. Independence of central and reflex thermoregulatory mechanisms.

Three patients who had suffered episodes of spontaneous hypothermia are described. Circulatory control was normal for their age but there was evidence of a persistent defect of thermoregulatory mechanisms. In all patients vascular thermoregulatory reflexes dependent upon peripheral receptors were active and in two patients reflex shivering could be obtained. There appeared, however, to be a failure of central thermoregulation as the vascular reflexes were active at abnormally low central temperatures and a fall in central temperature did not initiate shivering. It is concluded that in patients who have suffered spontaneous hypothermia there may be a persistent defect of central mechanisms subserving vasomotion and shivering, although thermoregulatory reflexes dependent upon peripheral receptors can be active. The reflex pathways for thermoregulation in man therefore have a separate integrity, physiologically independent of the central thermoregulatory mechanisms.

Aged↗
PubMed1976

Observations on the effect of salicylate in fever and the regulation of body temperature against cold.

Prostaglandins appear to be mediators, within the hypothalamus, of heat production and conservation during fever. We have investigated a possible role of prostaglandins in the nonfebrile rabbit during thermoregulation in the cold. Shorn rabbits were placed in an environment of 20 degrees C, and rectal and ear skin temperatures, shivering and respiratory rates were measured. A continuous intravenous infusion of leucocyte pyrogen was given to establish a constant fever of approximately 1 degree C, and after observation of a stable febrile temperature for 90 min, a single injection of 300 mg of sodium salicylate, followed by a 1.5 mg/min infusion was then given. After the salicylate infusion was begun, rectal temperature began to fall, and reached nonfebrile levels within 90 min. Shivering activity ceased, respiratory rates increased, and in two animals, ear skin temperature increased. When these same rabbits were placed in an environment of 10 degrees C, at a time they were not febrile, and an identical amount of salicylate was given, rectal and ear skin temperatures, shivering and respiratory rates did not change. These results indicate that prostagladins do not appear to be involved in heat production and conservation in the nonfebrile rabbit.

Animals↗
PubMed1986

Exercise suppression of thermoregulatory thermogenesis in warm- and cold-acclimated rats.

An evaluation was made of the effects of an acute exercise bout on nonshivering thermogenesis (NST) in cold-acclimated rats (4 degrees C for 6 weeks) and shivering thermogenesis in 24 degrees C-acclimated rats (24 degrees C for 6 weeks). Assessment techniques included indirect calorimetry during treadmill running and brown adipose tissue (BAT) mitochondrial guanosine diphosphate (GDP) binding immediately following a treadmill run. Calorimetric results for 24 degrees C-acclimated rats running at 4 degrees C indicated total substitution of shivering thermogenesis by exercise-derived heat. No difference in GDP-binding, an index of BAT nonshivering thermogenic activity, was observed between exercised and nonexercised 24 degrees C-acclimated rats. Calorimetric results for cold-acclimated rats running at 4 degrees C indicated a total suppression in the energy cost associated with NST, exercise-derived heat replacing or substituting for NST. Examining BAT properties in the exercised cold-acclimated rats revealed a significant 40% decrease in BAT mitochondrial GDP-binding. These results suggest that during running, metabolic heat due to the exercise totally replaces shivering in 24 degrees C-acclimated rats and totally replaces BAT nonshivering thermogenesis in cold-acclimated rats.

Acclimatization↗