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PubMed1990

[Secondary hypothermia with brain tumor in an elderly woman and the circadian rhythm of body temperature].

An elderly case of secondary hypothermia associated with brain tumor was reported. An 84-year old woman developed hypothermia. Although her rectal temperature remained below 37 degrees C, the circadian rhythm of rectal temperature was preserved. Brain computerized tomography (CT) and brain magnetic resonance imaging (MRI) revealed a solitary brain tumor involving the hypothalamus. It appears that her hypothermia may not be due to inability to thermoregulate but to stem from her abnormal target temperatures. Body temperature is normally controlled at around 37 degrees C, but in this patient thermoregulation might have been reset at a lower temperature.

Aged↗
PubMed2003

Ambient temperature influences core body temperature response in rat lines bred for differences in sensitivity to 8-hydroxy-dipropylaminotetralin.

Agonist-induced decrease in core body temperature has commonly been used as a measure of serotonin1A (5-HT(1A)) receptor sensitivity in mood disorder. The thermoregulatory basis for 5-HT(1A) receptor agonist-induced temperature responses in humans and rats remains unclear. Therefore, the influence of ambient temperature on 5-HT(1A) receptor-mediated decreases in core body temperature were measured in rat lines bred for high (HDS) or low (LDS) sensitivity to the selective 5-HT(1A) receptor agonist 8-hydroxy-dipropylaminotetralin (8-OH-DPAT). HDS and LDS rats were injected with either saline, 0.25 or 0.50 mg/kg 8-OH-DPAT at ambient temperatures of 10.5, 24, 30, or 37.5 degrees C, and core temperature was measured by radiotelemetry. For both lines, the thermic response to acute 8-OH-DPAT was greatest at 10.5 degrees C and decreased in magnitude as ambient temperature increased to 30 degrees C, consistent with hypothermia. HDS rats displayed a greater hypothermic response than LDS rats at 10.5, 24, and 30 degrees C. At 37.5 degrees C, LDS rats showed a lethal elevation of temperature in response to 0.50 mg/kg 8-OH-DPAT. All thermic responses to 8-OH-DPAT, including the lethality, were effectively blocked by pretreatment with the 5-HT(1A) receptor antagonist WAY100635, suggesting line differences in thermoregulatory circuits that are influenced by 5-HT(1A) receptor activation. Following repeated injection of 8-OH-DPAT, the magnitude of the hypothermic response decreased in both lines at 10.5 degrees C, but increased in HDS rats treated with 0.50 mg/kg 8-OH-DPAT at 30 and 37.5 degrees C. This pattern was reversed in HDS rats following 8-OH-DPAT challenge at 24 degrees C, suggesting that a compensatory thermoregulatory response accounts for changes in the hypothermic response to chronic 8-OH-DPAT.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1987

Effect of age and torpor on the circadian rhythms of body temperature, activity, and body weight in the mouse (Peromyscus leucopus).

Age-related alterations in homeostatic mechanisms, as measured by changes in circadian rhythms, have been reported in the literature. The purpose of the present study was to determine if changes in the circadian rhythms of motor activity, body temperature, and body weight occur with age in the long-lived mouse, Peromyscus leucopus, and to determine if the incidence of torpor (hypothermia) was age-dependent. Young and old mice were entrained to an LD 12:12 cycle, and then physiological and behavioral performance was monitored by a data-acquisition system. The major differences between the 6-month and 60-72-month age groups were the following. Significant episodes of torpor occurred in a high percentage of old mice at 0600 hr on consecutive days, but young mice showed no evidence of torpor when food was provided ab libitum. Torpor in young mice was found to occur only during starvation conditions. Old animals phase in and out of torpor over an interval of several days; high-amplitude rhythms and good synchronization of activity and temperature occurred when torpor was expressed, and low-amplitude rhythms, poor synchronization between temperature and activity, and a phase shift of body-weight acrophase occurred on days when torpor was not expressed. Significant changes in acrophase and amplitude occurred between individual animals and days in the old group; no significant change in acrophase and amplitude was observed in the young group. Population-mean cosinor analysis revealed a significant age-related decrease in amplitude and mesor, but no significant change in acrophase was found.

Aging↗
PubMed2000

Radiant warmers versus incubators for regulating body temperature in newborn infants.

BACKGROUND: This section is under preparation and will be included in the next issue. OBJECTIVES: To assess the effects of radiant warmers versus incubators (in the neonatal period) on fluid and electrolyte balance, neonatal morbidity and mortality. SEARCH STRATEGY: The standard strategy of the Cochrane Neonatal Review Group was used. This includes searches of the Oxford Database of Perinatal Trials, Medline, previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, journal handsearching mainly in the English language. SELECTION CRITERIA: All randomised or quasi-randomised trials in which radiant warmers are compared to incubators in a neonatal population. DATA COLLECTION AND ANALYSIS: Methods used to collect data from the included studies: Each author extracted data separately, then compared and resolved differences. A referee was sought for unresolved differences. Methods used to synthesise the data : Standard method of Neonatal Review Group with the use of weighted mean difference for outcome data measured on a continuous scale. MAIN RESULTS: A statistically significant increase in insensible water loss (IWL) was shown in neonates nursed under radiant warmers (WMD 0.94g/Kg/day, 95% CI 0.48, 1.41). A trend towards increased oxygen consumption which was not statistically significant was shown for the radiant warmer group (WMD 0. 27mL/kg/min, 95% CI -0.10, 0.63). A comparison of the radiant warmers with heat shields vs incubator without heat shields showed a similar trend for increased IWL in the radiant warmer group which was not statistically significant (WMD 1.00g/kg/day, 95% CI -0.10, 2. 10). No difference was shown in the rate of oxygen consumption when radiant warmers with heat shields were compared to incubators (WMD -0.05, 95% CI -0.84, 0.74). REVIEWER'S CONCLUSIONS: Radiant warmers result in increased IWL compared to incubators which needs to be taken into account when calculating daily fluid requirements.The results of this review do not provide sufficient evidence on important outcomes with the use of radiant warmers vs incubators to guide clinical practice. Further randomised controlled trials are required to assess the role of radiant warmers in neonatal care with particular attention to the extremely low birthweight population.

Body Temperature Regulation↗
PubMed1971

Pineal function in sparrows: circadian rhythms and body temperature.

Deep body temperature of the house sparrow, Passer domesticus, was monitored continuously by radio telemetry. Pinealectomy abolished the normal circadian rhythm of body temperature in constant darkness, and significantly altered the amplitude of body temperature rhythms entrained to light cycles. The body temperature minima of pinealectomized birds never fell as low as those of unoperated birds regardless of the light conditions; the temperature maxima of both normal and pinealectomized birds were higher in light than in darkness. In sparrows the pineal organ is essential to the normal function of the biological clock controlling both activity and body temperature rhythms and may be directly involved in thermoregulation.

Animals↗
PubMed1993

Effect of bundling and high environmental temperature on neonatal body temperature.

OBJECTIVE: The effect of bundling and ambient heat on newborn body temperature has not been systematically studied. It was hypothesized that bundling and warm environments can elevate the newborn's temperatures to the range that would prompt clinical concern of neonatal sepsis. METHODS: Twenty well, term newborns more than 1 day old were assigned to the control group (one blanket; 24.0 degrees C room) or the experimental group (five blankets and hat; 26.6 degrees C room). Continuous rectal probe temperatures were monitored over a 2 1/2-hour period. RESULTS: There were 8 control and 12 experimental newborns. The mean change in rectal temperature after 2 1/2 hours was -0.04 degrees C (SD +/- 0.23) in control newborns and +0.56 degrees C (SD +/- 0.12) in the treatment group (P < .0001, t test). Temperatures in the treatment group rose, after an initial half-hour lag, at a linear rate of 0.27 degrees C per hour without a plateau. Two newborns reached 38.0 degrees C, a rectal temperature that may raise concern of infection. CONCLUSIONS: Bundling and warm environments can elevate newborn body temperature to the "febrile" range in this age group. Physicians treating neonates with elevated temperature should ask about bundling and environmental conditions to differentiate endogenous from exogenous "fevers."

Body Temperature↗
PubMed1986

Body temperature and temperature gradients: changes during the estrous cycle and in response to ovarian steroids.

Rectal temperature, body weight, and vaginal membrane condition were monitored in female guinea pigs in order to determine the pattern and magnitude of changes in these variables across the estrous cycle and as a result of treatment with ovarian hormones. A thermistor probe was used to measure rectal temperatures at depths of 4 and 8 cm and to determine the temperature gradient between these two sites. Data collected across the estrous cycles of 18 intact females were aligned by day of vaginal membrane rupture, the estimated time of ovulation. Compared to measurements during the midluteal phase of the estrous cycle, rectal temperatures increased significantly one to three days prior to vaginal membrane rupture. In addition, a significant periovular decline was observed in the temperature gradient and in body weight. Treatment of ovariectomized females with 3 micrograms estradiol benzoate for 3 days (EB) followed by a single injection of 0.4 mg progesterone on the 4th day (P) led to biphasic changes in temperature. Compared to a control group which received injections of 0.2 ml corn oil vehicle for 4 consecutive days (OIL), EB significantly increased rectal temperature measured at the depth of 4 cm, but had no significant effect on measurements taken at a depth of 8 cm. The temperature difference between these two sites also decreased significantly. Rectal temperatures at both 4 cm and 8 cm sites dropped significantly following injection of progesterone. Ovarian hormones therefore have significant effects on body temperature of guinea pigs, effects which, in combination with other evidence, lead us to suggest that some of the observed temperature variations may be related to estrogen-induced changes in peripheral vasodilation or other mechanisms of heat loss.

Animals↗
PubMedDate not supplied

Dynamic thermal balance in the leaf-eared mouse: the interplay among ambient temperature, body size, and behavior.

Endotherms maintain constant body temperature through physiological and behavioral adjustments. Behavioral thermoregulation is an important factor influencing energy balance. We exposed the leaf-eared mouse, Phyllotis darwini, to temperatures corresponding to its natural thermal range and studied two forms of behavioral thermoregulation: diminishing surface to volume ratio by huddling and heat dissipation by increasing physical contact with the substrate (flattening). We predicted that at low ambient temperatures (T(a)) huddling would be used as a heat conservation mechanism and at high T(a) flattening would be used for heat loss. We simultaneously measured oxygen consumption (VO2) and flattening, in response to three independent factors: huddling, T(a), and body mass. Each experiment was a 6-h VO2 trial where five virgin females were measured at constant T(a). We performed this protocol for two body mass groups, small (ca. 40 g) and large (ca. 70 g), in a metabolic chamber. Treatments were groups with and without the ability to huddle at five different T(a), ranging from 5 degrees to 35 degrees C. A significant interaction between all three factors was found. Huddling and flattening were used as strategies for conserving or dissipating heat, respectively, and the shift between both strategies occurred at the lower limit of thermoneutrality. At T(a) below thermoneutrality, huddling was a more effective way of reducing metabolic requirements and was more efficient (H(E)) in small individuals than large individuals. So, by huddling, small individuals save more energy. At high T(a), flattening appeared to be an equally useful mechanism for heat loss, for both large and small animals.

Analysis of Variance↗
PubMed1987

Pirenperone effects on temperature preference and body temperature in maturing mice.

Thermoregulatory effects of the selective 5-HT2 antagonist pirenperone were studied 1 hr after IP injection in mice aged 1, 3, 5, 7 and 10 days postpartum. Compared with vehicle injected littermates, a dose of 0.16 mg/kg decreased temperature preference (T pref) on a thermal gradient at all ages. No significant effects were observed on body temperature (Tb) at any of the ages. An increased dose (0.48 mg/kg) caused no greater effect on T pref and no significant effect on Tb. These results indicate that Tb and T pref are separable on the basis of receptor pharmacology, and are discussed in relation to drug effects on 5-HT2 receptors.

Animals↗
PubMed2006

Body temperature variability (Part 1): a review of the history of body temperature and its variability due to site selection, biological rhythms, fitness, and aging.

Body temperature is a complex, non-linear data point, subject to many sources of internal and external variation. While these sources of variation significantly complicate interpretation of temperature data, disregarding knowledge in favor of oversimplifying complex issues would represent a significant departure from practicing evidence-based medicine. Part 1 of this review outlines the historical work of Wunderlich on temperature and the origins of the concept that a healthy normal temperature is 98.6 degrees F (37.0 degrees C). Wunderlich's findings and methodology are reviewed and his results are contrasted with findings from modern clinical thermometry. Endogenous sources of temperature variability, including variations caused by site of measurement, circadian, menstrual, and annual biological rhythms, fitness, and aging are discussed. Part 2 will review the effects of exogenous masking agents - external factors in the environment, diet, or lifestyle that can influence body temperature, as well as temperature findings in disease states.

Adult↗
PubMed1989

Sauna, shower, and ice water immersion. Physiological responses to brief exposures to heat, cool, and cold. Part III. Body temperatures.

Nine active winter swimmer men were subjected to four exposures each imitating a form of hot or cold exposures or their combination practiced among the Finns: (A) sauna and head-out ice water immersion; (B) sauna and 15 degrees C shower; (C) sauna and room temperature; (D) head-out ice water immersion and room temperature. All exposures were repeated and ended with recovery at room temperature. Body core and surface temperatures were recorded. One surface probe was placed between the scapulae to detect any signs of thermogenic activity by brown adipose tissue upon cold exposures. In the sauna control of core temperature was lost at esophageal temperature Tes 38 degrees C where the mean skin temperature exceeded the Tes. The brief ice water immersions did not disturb the thermal balance of the body core. The interscapular surface temperature recording provided circumstantial evidence of functioning thermogenic tissue in the area.

Adult↗
PubMed1976

A comparison of the effects of morphine and pethidine upon body temperature and the reversal of reserpine's effects upon body temperature in the mouse.

The effects of morphine and pethidine upon body temperature and upon the reversal of reserpine hypothermia in the mouse were investigated. Both morphine and pethidine produced a dose-dependent fall in body temperature, that of morphine being totally antagonized by nalorphine and partially by naloxone, while that of pethidine was antagonised by naloxone and enhanced by nalorphine. Both drugs reversed reserpine-induced hypothermia. The reversal by morphine, but not by pethidine, was partially antagonized by naloxone. Adrenalectomy prevented the reversal of reserpine hypothermia by pethidine but morphine produced a partial reversal. Ganglion blockade and alpha-and beta-blockade all prevented reversal of reserpine hypothermia by both drugs. The results are discussed with regard to differences between pethidine and morphine and possible involvement of opiate receptors.

Adrenalectomy↗