Body Temperature Of Animals Research Articles

Statistical power analysis: application to an investigation of dinosaur thermal physiology

It has been postulated that the variation in an animal's body temperature during different phases of bone deposition can be estimated from the variation in the ratio of two oxygen isotopes in phosphate recovered from its fossil. Using data from a fossil Tyrannosaurus rex skeleton, the previous researchers failed to reject the null hypothesis that the variation found in bones from the body core is significantly less than that found in the extremities; they also failed to reject the null hypothesis that the coldest and hottest parts of the body differed by less than 4 °C. This suggests that either both null hypotheses are true, or that they are false but the statistical tests used were not powerful enough to detect this. Here I use calculation of confidence intervals to differentiate between these two alternatives. In the first case, I find that the data are consistent with the variance in both the core and the extremity being up to 2.5 times that of the other. In the second case, I show that observations are consistent with temperature differences ranging from 2.6 °C to 6.4 °C. Hence, neither case provides any real support for the hypothesis that bone deposition in this specimen occurred under essentially thermostable conditions.

Stress fever magnitude in laboratory-maintained California ground squirrels varies with season

A previous study demonstrated that California ground squirrels ( Spermophilus beecheyi) living in the natural environment had, independent of season, a significantly higher mean diurnal body temperature ( T b) (39.6°C) than either summer (37.5°C) or winter (36.5°C) laboratory maintained animals. Based upon the previous study it has been suggested that California ground squirrels living in the natural environment may have an elevated set-point for body temperature in a manner analogous to a stress fever response. The present study was conducted to determine if season and/or duration of laboratory open-field exposure influenced the magnitude of laboratory open-field stress fever. If stress fever was involved to some extent in the higher body temperature observed in animals from the natural environment, laboratory maintained animals should exhibit a lower magnitude stress fever during the summer months and a higher magnitude stress fever during the winter months. It was hypothesized that laboratory maintained animals would exhibit the same set-point for stress fever T b independent of season, and that the duration of open-field exposure would not influence the magnitude of stress fever. Adult California ground squirrels were acclimated to an ambient temperature of 20±1.0°C under either LD 14:10 (summer) or LD 10:14 (winter) photoperiod conditions and individuals from both photoperiod conditions were exposed for periods of 2, 4, and 6 h to an open-field arena. An analysis of the data with a two-factor ANOVA demonstrated that season (photoperiod) significantly influenced the magnitude of the stress fever response (1.1±0.1°C for summer animals; 2.1±0.2°C for winter animals) while there was no significant influence of open-field exposure duration on stress fever magnitude. These results demonstrate that although the set-point for body temperature in unstressed laboratory maintained California ground squirrels varies with season, the set-point for body temperature in open-field stressed animals does not vary with season. These data lend support to the hypothesis that something like stress fever may play some role in the higher body temperature observed in California ground squirrels living in the natural environment.

Oral Antibiotics reduce Body Temperature of Healthy Rabbits in a Thermoneutral Environment

Nonabsorbable oral antibiotics, which reduce gut flora, decrease the daytime and night-time body temperatures of rats and mice. We investigated whether oral antibiotics would also lower the body temperature of healthy rabbits. Six rabbits received neomycin sulphate in their drinking water for ten days, and seven rabbits received a mixture of chloramphenicol and dihydroxystreptomycin for six days. Body temperatures, recorded using intra-abdominal radiotelemeters, decreased significantly, by 0.2-0.3 degree C, after three days of antibiotic treatment in both groups of rabbits. The drop in body temperature was transient; after six days body temperatures returned to pre-antibiotic levels. Antibiotic treatment had no effect on either the acrophase or the amplitude of the circadian rhythm in body temperature. Oral antibiotics therefore reduce body temperature of rabbits, without influencing the circadian rhythm in body temperature. Our results are consistent with the hypothesis that an agent arising from intestinal bacteria sustains an elevated body temperature in healthy animals.

The energetic cost of arousal from torpor in the marsupial Sminthopsis macroura: benefits of summer ambient temperature cycles.

The costs of arousal from induced torpor were measured in the striped-faced dunnart (Sminthopsis macroura, ca. 25 g) under two experimental ambient temperature cycles. The sinusoidal-type temperature cycles were designed to evaluate the effects of passive, ambient temperature heating during arousal from torpor in these insectivorous marsupials. It was hypothesised that diel ambient temperature cycles may offer significant energy savings during arousal in animals that employ daily torpor in summer as a response to unpredictable food availability. The cost of arousal in animal in which passive, exogenous heating occurred was significantly lower than that in animals not exposed to an ambient temperature cycle. The total cost of all three phases of torpor (entry maintenance and arousal) was almost halved when animals were exposed to an ambient heating cycle from 15 degrees C to 25 degrees C over a 24-h period. In all animals, irrespective of the experimental ambient temperature cycle employed, the minimum torpor body temperature was 17-18 degrees C. The body temperature (Tb) of animals exposed to exogenous heating increased from the torpor Tb minimum to a mean value of 22.59 degrees C before endogenous heat production commenced. This relatively small increase in Tb of ca. 5 degrees C through 'free' passive heating was sufficient to account for the significant ca. three-fold decrease in the cost of arousal and may represent an important energetic aid to free-ranging animals.

Hypophagia-induced hypometabolism during experimental anaemia in rats

Several investigators have reported a drop in oxygen (O2) consumption (VO2) and body temperature in laboratory animals during normobaric or hypobaric hypoxia. Hypophagia, with normal efficiency of protein utilisation for growth, was also observed. It has recently also been observed that hypometabolism is present during anaemic hypoxia. The present study was designed to test the experimental hypothesis that anaemic hypoxia induces hypometabolism secondary to hypophagia. Episodes of anaemia were created in adult male rats by either blood withdrawal through cardiac puncture (haemorrhagic anaemia) or phenylhydrazine administration (haemolytic anaemia). Haematrocrit, VO2, and food consumption, as indirect estimations of the level of anaemia, energy production, and appetite, respectively, were serially measured in all animals during 7 days (acute experiments) or 17 days (chronic experiments). Positive correlations were found between the three parameters during development of and recovery from anaemia during each anaemic episode. When the amount of food offered to non-anaemic rats was equalised to that freely eaten by anaemic rats, VO2 dropped in the former to almost the level found in the latter. Body composition changed during chronic anaemia because of a decrease in the lipid fraction of the body. The results confirmed the working hypothesis that hypometabolism, which has been considered as an immediate, emergency-type response to both hypoxic and anaemic hypoxia, can be considered as a response secondary to hypophagia because of depressed appetite. How appetite is adapted to the mechanisms which control O2 convection and O2 availability is not known at present.

Effect of acute verapamil treatment on body temperature in nucleus basalis magnocellularis-lesioned rats

Our recent studies suggest that lesions of the nucleus basalis magnocellularis (nbm) in rats induce a significant decrease of core body temperature in standard laboratory conditions. Considering the importance of calcium homeostasis in thermoregulation, as well as in the pathogenesis of neurodegeneration, the aim of the present study was to investigate the effect of acute verapamil treatment on body temperature in nbm-lesioned rats. The body temperature was registered before and 30 min after verapamil was subcutaneously administered (1.0, 2.5, 5.0 and 10.0 mg/kg). Verapamil did not change body temperature in control animals. However, verapamil in doses of 2.5 and 5.0 mg/kg significantly increased the core body temperature in nbm-lesioned rats nearly up to the temperature of control animals. Findings that verapamil in doses of 1.0 and 10.0 mg/kg did not change body temperature in nbm-lesioned suggest the existence of an inverted U-shape curve in its effect.

TETRAD: an on-line telematic surveillance system for animal transports

A new concept for on-line surveillance of animal transports is presented, comprising telemetry and wireless data communication. The concept has two major objectives: (1) to improve animal disease prevention and control and (2) to enable monitoring of animal welfare during transport. The system allows on-line collection on the transport lorry of data with respect to animal identification , body temperature and geographical position. Concept and prototype system are described. Performance tests on data collection and transmission showed the technical feasibility of the prototype system, both under laboratory and semi-practical conditions. Necessary improvements and future use of the system are discussed.

L-threonine injection into PPC modifies food intake, lateral hypothalamic activity, and sympathetic discharge.

Food intake and the firing rate of lateral hypothalamic neurons and nerves innervating interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures, were monitored in male Sprague-Dawley rats fed a threonine-free diet. These variables were measured before and after a bilateral injection of L-threonine (2 nmol into each side) into the prepiriform cortex (PPC). The same variables were also monitored in 1) rats fed a threonine-free diet and injected with saline, 2) animals fed a standard diet and injected with L-threonine, and 3) rats fed a standard diet and injected with saline. The results showed that injection of L-threonine into PPC increases food intake and firing rate of lateral hypothalamic neurons, whereas it decreases the sympathetic discharge and body temperature in animals fed a threonine-free diet. No changes were found in the animals fed a standard diet. These findings suggest a correlation between 1) threonine level in the PPC and 2) lateral hypothalamic activity and sympathetic discharge to IBAT.

Patterns of Body Temperature, Activity, and Reproductive Behavior in a Tropical Murid Rodent, Arvicanthis niloticus

McElhinny, T. L., L. Smale and K. E. Holekamp. Patterns of body temperature, activity, and reproductive behavior in a tropical murid rodent, Arvicanthis niloticus. Physiol Behav 62(1) 91–96, 1997.—Nile grass rats (Arvicanthis niloticus), are murid rodents from tropical Africa that exhibit diurnal patterns of wheel-running. In the present paper we describe the temporal organization of several other behaviors in these animals, as well as daily rhythms in their body temperature. In the first experiment, we characterized rhythms of gross motor activity and core body temperature in four adult females implanted with telemetry transmitters and kept on a 12:12 light:dark (LD) cycle. In all animals body temperature and gross motor activity were clearly diurnal, with peaks often occurring around dawn and dusk. In the second experiment we recorded the times of mating and parturition in eight mating couples housed in a 12:12 LD cycle. We monitored animals 24 h a day using a time-lapse video recording system, beginning when males and females were paired, and ending after the birth of the second litter and the associated post-partum copulation. Mating almost always began just before the lights came on, and parturition generally occurred in an “anticrepuscular” pattern, outside of the periods around dawn and dusk. Thus, these animals exhibit an interesting mosaic of temporal adaptations, with some crepuscular tendencies expressed within a predominantly diurnal pattern.

Involvement of prostaglandins in cachexia induced by T-cell leukemia in the rat

We have previously demonstrated that experimentally induced T-cell leukemia in the rat results in a rapid and severe cachexia. This weight loss is largely due to a reduction in food intake, but is also accompanied by inappropriately high rates of energy expenditure. Increases in resting oxygen consumption (V̇ o 2) of 25% to 35% above the levels of pair-fed animals were observed over the period of weight loss. The present study investigated the possible involvement of prostaglandins in the cachexia induced by T-cell leukemia in the rat. Acute systemic injection of the cyclo-oxygenase inhibitors (indomethacin 1 mg/kg or flurbiprofen 1 mg/kg intraperitoneally [IP]) significantly reduced (by 14% and 10%, respectively) the increase in metabolic rate and also reversed the elevated body temperature of leukemic animals. Intracerebroventricular (ICV) injection of indomethacin (0.2 mg/kg) had only modest effects on the increase in temperature or hypermetabolism of leukemic animals. Long-term daily injection of indomethacin or flurbiprofen (1 mg/kg/d IP) had no significant effect on food intake or body weight of leukemic animals, and neither treatment significantly affected disease status. Indomethacin significantly reduced the decline in epididymal fat pad weight of leukemic animals. These data indicate that prostaglandins, produced peripherally, are involved in the acute hypermetabolism associated with T-cell leukemia, but have little or no effect on the hypophagia or body weight loss of leukemic rats.

ENERGETIC CONSEQUENCES OF FIELD BODY TEMPERATURES IN THE GREEN IGUANA

We investigated body temperatures of free-ranging green iguanas (Iguana iguana) on Curacao (Netherlands Antilles), and how metabolic costs and benefits of food processing affect body temperatures. Body temperatures of free-living iguanas were mea-sured by radio telemetry. We also used a model, with activity data and operative temperature from taxidermic mounts as inputs, to estimate body temperature of free-ranging animals. Estimated body temperature was highly correlated with telemetered body temperature (mean difference 0.8°C). Thus, our model for estimating lizard body temperatures may be useful in field studies where telemetry is not possible. Data from both telemetry and estimation with the model showed that green iguanas maintained relatively constant body temperatures (minimum 32.9 ± 1.4°C; maximum 36.6 ± 2.9°C; mean ±1 SD) during the midday period (0945-1545). Temperature measurements of taxidermic mounts and ambient air showed that body temperatures between 29°C and 40.5°C could readily be attained on Curacao. Hence, the range of potential body temperatures was much greater than the range of actually achieved body temperatures. Thermoregulatory behavior, food intake, and locomotor activities were recorded along with temperature measurements. Relations between body temperature, daily metabolizable energy intake (MEI), and resting metabolic rate (RMR) were used to examine whether or not observed body temperatures coincide with temperatures at which energy gain from ingested food is high. Our data show that, in these herbivorous reptiles, food intake and digestion explain most of the variation in the observed field body temperatures.

Energetic Consequences of Field Body Temperatures in the Green Iguana

We investigated body temperatures of free-ranging green iguanas (Iguana iguana) on Curaçao (Netherlands Antilles), and how metabolic costs and benefits of food processing affect body temperatures. Body temperatures of free-living iguanas were measured by radio telemetry. We also used a model, with activity data and operative temperature from taxidermic mounts as inputs, to estimate body temperature of free-ranging animals. Estimated body temperature was highly correlated with telemetered body temperature (mean difference 0.8°C). Thus, our model for estimating lizard body temperatures may be useful in field studies where telemetry is not possible. Data from both telemetry and estimation with the model showed that green iguanas maintained relatively constant body temperatures (minimum 32.9 ± 1.4°C; maximum 36.6 ± 2.9°C; mean ± 1 sd) during the midday period (0945–1545). Temperature measurements of taxidermic mounts and ambient air showed that body temperatures between 29°C and 40.5°C could readily be attained on Curaçao. Hence, the range of potential body temperatures was much greater than the range of actually achieved body temperatures. Thermoregulatory behavior, food intake, and locomotor activities were recorded along with temperature measurements. Relations between body temperature, daily metabolizable energy intake (MEI), and resting metabolic rate (RMR) were used to examine whether or not observed body temperatures coincide with temperatures at which energy gain from ingested food is high. Our data show that, in these herbivorous reptiles, food intake and digestion explain most of the variation in the observed field body temperatures.

A test of the accuracy of operative temperature thermometers for studies of small ectotherms

1. 1. Various devices have been used to estimate the equilibrium body temperature of ectotherms occupying natural environments. We tested the accuracy of such devices under a range of conditions. 2. 2. We measured body temperatures of lizards ( Sceloporus magister) exposed to short-wave radiation under varying convective conditions and compared these to temperatures of hollow metal casts duplicating the animal's shape and reflectivity, as well as to the temperatures of cylinders similar to those used by other workers. 3. 3. Casts equilibrated within 2–3°C of live animals, yielding errors of 14–37% of the radiation-produced elevation of body temperature. 4. 4. Various cylinders differed from animal body temperature more than lizard casts did, producing errors equally 33–53% of the radiation-produced elevation. 5. 5. It is imperative that workers using operative-temperature thermometers experimentally confirm the adequacy of the devices they use for the range of conditions encountered within a specific analysis.

Studies on Some Psychopharmacological Actions ofMoringa oleifera Lam. (Moringaceae) Leaf Extract

The methanol extract of the leaves of Moringa oleifera Lam. was investigated for some psychopharmacological actions in animals. The extract was found to produce a significant alteration in general behavioural pattern by head dip test, Y-maze test, evasion test, and reduction in muscle relaxant activity by rotarod test, chimney test and traction test. Beside these, the extract also potentiated pentobarbitone induced sleeping time and lowered body temperature in experimental animals.

Use of animal models in peptic ulcer disease.

Considerable progress has been made in the understanding of the formation of gastric erosions by the use of animals. The role of gastric acid secretion in their pathogenesis has been clarified. Gastric erosions are associated with the presence of acid in the stomach and slow gastric contractions. With several different experimental procedures, the animal's body temperature falls; preventing the fall averts erosions. A fall in body temperature or exposure to cold are associated with the secretion of thyrotropin-releasing hormone (TRH), and both increased and decreased concentration of corticotropin-releasing factor (CRH) in discrete regions of rat brains. Thyrotropin-releasing hormone when injected into specific sites in the brain produces gastric erosions and increases acid secretion and slow contractions, whereas CRH has the opposite effects. One of the major sites of interaction of the two peptides is in the dorsal motor complex of the vagus nerve. Thyrotropin-releasing hormone increases serotonin (5-HT) secretion into the stomach. Serotonin counter-regulates acid secretion and slow contractions. Many other peptides injected into discrete brain sites stimulate or inhibit gastric acid secretion.

Effects of hypothalamic lesions on the body temperature rhythm of the golden hamster.

The effects of electrolytic and neurotoxic lesions of the suprachiasmatic nucleus (SCN) and preoptic area (POA) of the anterior hypothalamus were studied by temperature telemetry in the golden hamster (Mesocricetus auratus) examined under two ambient temperature conditions: 24 degrees C and 6 degrees C. Although attempted lesions with microinjections of ibotenic acid proved unsuccessful, electrolytic lesions of the SCN eliminated the circadian rhythm of body temperature (CRT), indicating an active role of this nucleus in the establishment of the CRT. Electrolytic lesions of the POA, but not of the SCN, resulted in an increased amplitude of the CRT at both 24 degrees C and 6 degrees C, with the lower ambient temperature enhancing this amplitude change to a greater extent. These results suggest that the POA and the SCN are independently responsible for the homeostatic and circadian regulation of body temperature, respectively. The increased amplitude of the CRT after POA lesions raises the possibility that the thermoregulatory system may oppose rather than defend the circadian control of body temperature in normal animals, which is consistent with several recent behavioral findings.

Prey selection by insectivorous bats: are essential fatty acids important?

Although body temperatures of torpid animals fall well below the melting point of many fats, body fats must remain fluid to be metabolized. High levels of dietary essential fatty acids (EFAs) may facilitate the use of torpor, as an increase in the proportion of EFAs in body fat decreases the melting point of body fats. The purpose of our study was to determine the importance of EFAs in the diets of four reproductive classes (males and nonreproductive pregnant, and lactating females) of three species of insectivorous bats: Myotis yumanensis, M. lucifugus, and M. californicus. Males are expected to use torpor frequently and, therefore, should select a diet high in EFAs. We ranked insect orders found in bat feces (diet) and light-suction-trap samples (availability) on the basis of their linoleic acid (a common EFA) content. We used these ranks to obtain estimates of the linoleic acid content of bats' diets, i.e., "dietary fat scores," and of available insects' "trap sample fat scores," respectively. Dietary fat scores did not differ significantly among reproductive classes. As predicted, the average fat score of males was high relative to the fat score of available insects. However, fat scores of male M. lucifugus and M. yumanensis were significantly greater than those of male M. californicus. Thus, EFAs do not appear to be as important in the diet of the latter species, suggesting that torpor may not be employed regularly.

Restraint, but not frustration, induces prostaglandin-mediated hyperthermia in pigs

Three experiments were carried out to investigate stress hyperthermia in prepubertal pigs. Experiment 1 examined the effect of frustrative nonreward (psychological stress) on deep body temperature in animals ( n = 7) trained to make operant responses for food following a 17.5-h period of deprivation. There was no change in body temperature when the feeders were switched off whereas there was a small increase (NS) during normal operant feeding that might be attributable to physical exertion. In Experiment 2, the effects of 15-min physical restraint (snaring) were examined in the same group of animals. This procedure induced a significant ( p < 0.01) rise in core temperature that was completely abolished by prior administration of a cyclooxygenase inhibitor (indomethacin, 2 mg/kg given intravenously). The final experiment investigated the effects of snaring on plasma cortisol concentrations. Blood samples were taken from indwelling catheters in pigs ( n = 5) subjected to 15-min restraint with, or without, indomethacin pretreatment. Snaring produced a significant ( p < 0.001) increase in cortisol release that was not affected by the administration of indomethacin. These results suggest that snaring, a physical stress that may also have energy expenditure components, induces a prostaglandin-mediated hyperthermic response in the growing pig.

Soluble interleukin‐6 (IL‐6) receptor augments central effects of IL‐6 in vivo

The pleiotropic cytokine interleukin-6 (IL-6) controls both the peripheral and central components of the acute-phase response. These activities are mediated via the IL-6 membrane receptor, but probably also via agonistic soluble IL-6 receptors (sIL-6Rs). In the present study we conducted dose-response experiments with rats that were intracerebroventricularly i.c.v.) injected with recombinant human IL-6 and sIL-6R and determined body temperature, locomotor activity, food intake, and water consumption using radiotelemetry and continuous recordings of feeding and drinking. IL-6 injected i.c.v. at 1, 10, and 100 ng increased body temperature and decreased locomotor activity and food intake, but it did not affect water consumption. When 10 ng sIL-6R, which lacked detectable biological activity, was injected i.c.v. 1 h before 1 ng IL-6, the central effects of IL-6 were enhanced and prolonged, and this was not due to endotoxin contamination of the recombinant proteins. Our data suggest that IL-6 plays an important role in the regulation of body temperature, general activity, and food intake in sick animals. Moreover, we have shown for the first time that it is possible to potentiate the effects of a mediator in vivo by administration of the corresponding receptor, which is a novel pharmacological tool for increasing receptor capacity.

Trifluopromazine Late Preventive Effects on Carbon Tetrachloride-Induced Liver Necrosis

Trifluopromazine (TFPro) administration to rats (50 mg/kg, ip) 30 min before or 6 or 10 hr after CCl 4 treatment (1 ml/kg ip in olive oil) partially prevented necrogenic effects of this compound at 24 hr. TFPro has only minor effects on the covalent binding (CB) of CCl 4-reactive metabolites to cellular constituents and even an enhancing action on CCl 4-promoted lipid peroxidation (LP). Determination of TFPro levels in liver 1 and 3 hr after administration by gas chromatography/mass spectrometry showed its presence in that tissue at concentrations well above those needed for calmodulin (CaM) inhibitory effects of this drug. TFPro lowered body temperature in CCl 4-treated animals during the 24-hr observation period. Protective effects of TFPro at 6 or 10 hr, when most of the CB and all of the LP has already occurred, suggest but do not prove a role for CaM in late stages of CCl 4-induced necrogenic effects. Decreases in the body temperature of CCl 4-poisoned animals provoked by TFPro might also play a role in the preventive actions of this drug.