Monitoring Of Core Body Temperature Research Articles

Sleep and Circadian Rhythms in Spousally Bereaved Seniors

A laboratory study of sleep and circadian rhythms was undertaken in 28 spousally bereaved seniors (≥60 yrs) at least four months after the loss event. Measures taken included two nights of polysomnography (second night used), ∼36 h of continuous core body temperature monitoring, and four assessments of mood and alertness throughout a day. Preceding the laboratory study, two‐week diaries were completed, allowing the assessment of lifestyle regularity using the 17‐item Social Rhythm Metric (SRM) and the timing of sleep using the Pittsburgh Sleep Diary (PghSD). Also completed were questionnaires assessing level of grief (Texas Revised Inventory of Grief [TRIG] and Index of Complicated Grief [ICG]), subjective sleep quality (Pittsburgh Sleep Quality Index [PSQI]), morningness‐eveningness (Composite Scale of Morningness [CSM]), and clinical interview yielding a Hamilton Depression Rating Scale (HDRS) score. Grief was still present, as indicated by an average TRIG score of about 60. On average, the bereaved seniors habitually slept between ∼23:00 and ∼06:40 h, achieving ∼6 h of sleep with a sleep efficiency of ∼80%. They took about 30 min to fall asleep, and had their first REM episode after 75 min. About 20% of their sleep was in Stage REM, and about 3% in Stages 3 or 4 (slow wave sleep). Their mean PSQI score was 6.4. Their circadian temperature rhythms showed the usual classic shape with a trough at ∼01:00 h, a fairly steep rise through the morning hours, and a more gradual rise to mid‐evening, with an amplitude of ∼0.8°C. In terms of lifestyle regularity, the mean regularity (SRM) score was 3.65 (slightly lower than that usually seen in seniors). Mood and alertness showed time‐of‐day variation with peak alertness in the late morning and peak mood in the afternoon. Correlations between outcome sleep/circadian variables and level of grief (TRIG score) were calculated; there was a slight trend for higher grief to be associated with less time spent asleep (p=0.07) and reduced alertness at 20:00 h (p=0.05). Depression score was not correlated with TRIG score (p>0.20). When subjects were divided into groups by the nature of their late spouse's death (expected/after a long‐term chronic illness [n=18] versus unexpected [n=10]), no differences emerged in any of the variables. In conclusion, when studied at least four months after the loss event, there appears to be some sleep disruption in spousally bereaved seniors. However, this disruption does not appear to be due to bereavement‐related disruptions in the circadian system.

Elevated body temperatures of adult female leopard sharks, Triakis semifasciata, while aggregating in shallow nearshore embayments: Evidence for behavioral thermoregulation?

The leopard shark, Triakis semifasciata, is an abundant nearshore elasmobranch, ranging from Baja California, Mexico to Oregon, USA. Mature female leopard sharks have been observed aggregating in shallow embayments throughout California; however, it is unclear why only females aggregate in these shallow areas. The goal of this study was to determine if mature female leopard sharks selectively occupy the warmest areas of a shallow embayment, if free-ranging leopard sharks' body temperatures are significantly warmer during the day than at night, and to quantify temporal use of these shallow habitats. Visual observations of sharks' fine-scale movements within the shallows of Big Fisherman's Cove Marine Life Refuge (Santa Catalina Island) aggregation site indicated that sharks preferred the warmest areas of the embayment and moved to warmer locations over the course of the day ( p < 0.05). Active and passive acoustic tracking, along with archival transponder technology (Vemco: V13, V13-R256, VX32TP-CHAT tags respectively) of 16 sharks caught and tagged within this aggregation were used to monitor core body temperature, swimming depth, and movements. Sharks had significantly higher core body temperatures in the late afternoon (1700 h–2000 h) during the summer, showed increased fidelity to thermal refuges during the day and increased movement away from these refuges at night ( χ 2, p < 0.05). Seasonal variations in warm, shallow water usage were also observed. Elevated core body temperature of mature female leopard sharks using warm shallow embayments will likely augment metabolic and physiological functions such as digestion, somatic growth, and possibly reproduction.

Ionotropic glutamate receptors in the dorsomedial hypothalamus mediate stress‐induced hyperthermia

Stress-induced hyperthermia is a well-known component of the response to stress in mammals. Neurons in the dorsomedial hypothalamus (DMH) play an important role in thermoregulatory adjustments, but the role of the DMH in stress-induced hyperthermia has yet to be examined. We have previously shown that microinjection of non-selective ionotropic glutamate receptor (iGR) antagonists into the DMH suppresses stress-induced tachycardia. Here we tested the hypothesis that iGRs in the DMH mediate the increase in core body temperature seen in experimental stress in conscious rats. Male SD rats were instrumented with bilateral guide cannulas targeting the DMH and intraperitoneal telemetric transmitters for monitoring core body temperature. Cage switch evoked significant increases in core body temperature that were abolished by prior microinjection of the non-selective iGR receptor antagonist, kynurenic acid (10nmol/side), into the DMH. Similar microinjection of a cocktail of an N-methyl-D-aspartate (NMDA) iGR antagonist, 2-amino-phosphonopentanoic acid, (APV; 200pmol/side) and a non-NMDA iGR antagonist, 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)-quinoxaline-2,3-dione, (NBQX; 100pmol/side) also abolished these increases. These findings suggest that stress-induced hyperthermia may be mediated by iGRs in the DMH. (Supported by USPHS Grants MH 65697 and NS 19883, and F31 NS052929 to MYM)

A biocompatible microdevice for core body temperature monitoring in the early diagnosis of infectious disease

The early diagnosis of microbial infection is critical to the clinical instigation of effective post-exposure prophylaxis or therapy. However, diagnosis of infection is often attempted only when there are overt clinical signs, and for some of the serious human pathogens, this may jeopardize the efficacy of therapy. We have used a miniaturised sealed, implantable transponder incorporating a calibrated temperature sensor with an external receiver system, to monitor core body temperature (Tc) remotely. We have observed early changes in the diurnal rhythm of Tc, after infection of mice with bacterial pathogens. Changes in Tc preceded overt clinical signs by 3-10 h following challenge with Yersinia pestis, which causes acute infection, In contrast, changes in Tc were detected 11 days before clinical signs in mice exposed to Burkholderia pseudomallei, which causes a chronic syndrome. Significantly, mice pre-vaccinated against Y.pestis infection showed only slight and transient disruption to the diurnal rhythm for Tc, in the absence of clinical signs, when challenged with 10(6) median lethal doses of Y.pestis. This remote monitoring technology could be used to monitor changes in more than one physiological parameter and extrapolation of these data to the clinic would define the available therapeutic window in which diagnosis and post-exposure prophylaxis could be instigated, after a suspected exposure.

Quantitative EEG and neurological recovery with therapeutic hypothermia after asphyxial cardiac arrest in rats

We test the hypothesis that quantitative electroencephalogram (qEEG) can be used to objectively assess functional electrophysiological recovery of brain after hypothermia in an asphyxial cardiac arrest rodent model. Twenty-eight rats were randomly subjected to 7-min (n = 14) and 9-min (n = 14) asphyxia times. One half of each group (n = 7) was randomly subjected to hypothermia (T = 33 °C for 12 h) and the other half (n = 7) to normothermia (T = 37 °C). Continuous physiologic monitoring of blood pressure, EEG, and core body temperature monitoring and intermittent arterial blood gas (ABG) analysis was undertaken. Neurological recovery after resuscitation was monitored using serial Neurological Deficit Score (NDS) calculation and qEEG analysis. Information Quantity (IQ), a previously validated measure of relative EEG entropy, was employed to monitor electrical recovery. The experiment demonstrated greater recovery of IQ in rats treated with hypothermia compared to normothermic controls in both injury groups (P < 0.05). The 72-h NDS of the hypothermia group was also significantly improved compared to the normothermia group (P < 0.05). IQ values measured at 4 h had a strong correlation with the primary neurological outcome measure, 72-h NDS score (Pearson correlation 0.746, 2-tailed significance <0.001). IQ is sensitive to the acceleration of neurological recovery as measured NDS after asphyxial cardiac arrest known to occur with induced hypothermia. These results demonstrate the potential utility of qEEG-IQ to track the response to neuroprotective hypothermia during the early phase of recovery from cardiac arrest.

Establishing the Evidence Base

The mission of the UK Army Training and Recruiting Agency (ATRA) is to deliver the required number of appropriately trained and motivated officers (∼700/year) and soldiers (∼9000/year) to meet the operational requirements of the British Army. To support this mission, ATRA has a multidisciplinary Occupational Medicine/Physiology team whose task is to provide evidence-based support to Army recruiting and training policy and practice. PURPOSE: To summarise the approach, findings and recommendations of research over the last 6-years. METHODS: Research is agreed and commissioned by ATRA Operating Divisions (the trainers). Initially, data on training injuries, the rate of Medical Discharge (MDt) and Remedial Instructor (RIt) referral were obtained. Recent research has fallen into three main areas. Firstly, work has been undertaken to develop job-related Physical Selection Standards for Recruits (PSS(R)) and Officers (PSS(O)). Secondly, work has been undertaken to quantify the progression of the absolute (Energy Expenditure (EE), Physical Activity Counts (PAC)) and relative (% Heart Rate Reserve (%HRR)) physical demands of various initial training regimes. Finally, specific research has been undertaken to quantify the degree of hyperthermia experienced by trainees. RESULTS: Whilst PSS(R) was implemented in 1998 and re-validated in 2003, PSS(O) is still under development. Together these processes will ensure that, on completion of initial training, personnel have the requisite physical capacity for their chosen trade and/or profession, thereby maximising their effectiveness and minimising the risk of morbidity during subsequent training and operations. The results of these studies have led to widespread change in training practice and policy and an increase in dietary provision for trainees. All female recruits are soon to be trained in single-gender platoons. The ability to monitor core body temperature accurately under field conditions has allowed us to develop environmental limits for bespoke activities, modify events to minimise the degree of hyperthermia and better manage heat illness. CONCLUSION: Whilst it is difficult to establish cause and effect since the implementation of the recommendations from this research, there has been a reduction in the: incidence of MDt in female recruits (11.1% to 3.2%, P<0.01); cross-gender odds ratio (F:M) for MDt (7.5 to 2.9, P<0.01); incidence of MDt among Parachute Regiment recruits (14.4% to 5.1%, P<0.01); incidence of heat illness during officer cadet training (2.0% to 0.1%). This work was sponsored by the UK Ministry of Defence (Army).

A comparison of auricular, rectal and pulmonary artery thermometry in dogs with anesthesia‐induced hypothermia

AbstractObjective: To determine if a correlation exists among auricular, rectal and pulmonary artery (PA) temperatures in hypothermic dogs.Design: Prospective study.Setting: Angiography suite at a college of veterinary medicine.Animals: Sexually intact female research hounds (13.9–25.4 kg; n=8).Measurements and main results: Dogs were anesthetized for instrumentation with a percutaneously placed, thermistor‐tipped, PA catheter. Anesthesia was maintained until the core body temperature decreased to 36.6°C (97.8°F). Anesthesia was discontinued, and auricular and rectal temperatures were obtained every 15 minutes until the PA temperature reached 38.3°C (100.9°F). A strong correlation was noted among the 3 methods of temperature measurement (P&lt;0.001; R≥0.846). No statistical difference was detected among measurement methods at baseline, the minimum temperature attained, nor the median temperature attained. However, at the maximum temperature attained, auricular measurements (37.7±0.4°C or 99.8±0.7°F) were lower than either the rectal (38.3±0.3°C or 100.9±0.5°F) or PA (38.3±0.3°C or 100.9±0.5°F) temperature measurements (P=0.001).Conclusion: There is a strong correlation among rectal, auricular and PA temperatures. Auricular temperature may be used to monitor core body temperature during postoperative rewarming; however, it might be slightly lower than core temperature as normothermia is reached.

95 Monitoring core body temperature in infantry soldiers and airfield defence guards

95 Monitoring core body temperature in infantry soldiers and airfield defence guards

A model of fescue toxicosis: Responses of rats to intake of endophyte-infected tall fescue1,2

A study was conducted to develop a model for fescue toxicosis using rats fed a diet containing endophyte-infected tall fescue seed (E+). Rats implanted with telemetric transmitters to continuously monitor core body temperature (Tc) and activity were housed at thermoneutrality (21 degrees C) and were fed a diet containing endophyte-free fescue seed (E-). After 2 wk, they were assigned to either E+ or E- diets and initially maintained at thermoneutrality (preheat) for 8 d. They were then exposed to heat stress (31 degrees C) for 22 d, followed by 1 wk of recovery at thermoneutrality (post-heat). Body weight and feed intake were measured daily. Rats receiving the E+ diet showed decreased feed intake (P = 0.001) and weight gains (P = 0.003) during the preheat period. The decrease in Tc from the pre-treatment level was greater in E+ than in E- rats during the preheat (P = 0.001) and postheat (P = 0.001) periods. With heat stress, both groups showed parallel decreases in feed intake. The increase in Tc from pre-heat to heat conditions was greater in E+ vs. E- rats (P = 0.001). Activity level was lower in E+ than in E-rats during heat stress (P = 0.009) and postheat (P = 0.037) periods. These results show that the rat model for fescue toxicosis is extremely useful because many of the observed responses to E+ diet are similar to those noted for cattle, and additional variables that are difficult to measure in cattle, such as activity, can be easily evaluated.

Measurement of horse core body temperature

Horse core body temperature (CBT) was monitored by three methods to compare three distinct physiological locations (blood temperature, BT; rectal temperature, RT; and telemetry-based gastrointestinal temperature, GT). Calibrated results indicate that CBT was different for each location (0.5 °C greater GT vs. RT; 1.0 °C greater GT vs. BT). The diurnal CBT average, minimum, and maximum were 38.0, 37.6, and 38.5 °C, respectively; and the telemetry-based system for measuring GT applied in this study is an acceptable alternative method for monitoring core body temperature in horses.

Validation of a new telemetric core temperature monitor

The purpose of this study was to validate the accuracy and acceptability of the new VitalSense ® telemetric physiological monitoring system (Mini Mitter Co., Inc., Bend, OR). It consists of a receiver/monitor and a thermistor-based ingestible capsule for core body temperature measurement. For comparison, each subject was also monitored with a standard thermistor probe inserted 11 cm beyond the anal sphincter (Mini-Logger ® Series 2000). Both the measurement systems have specified accuracy of ±0.1 °C. Ten volunteers, four females, six males, mean age 51.1±11.8 years, gave informed consent to wear the two systems for the duration of the passage of the temperature capsule through their digestive tracts. Minute-by-minute comparisons were made between the temperatures recorded by the two systems. Parameters reported include: average transit time of the capsule; temperature at each minute of the experiment; mean difference in temperature at each time point; correlation coefficient for the two temperature measurements; and number of missed data points for each system. Mean capsule transit time was 48.6±35.5 h with a range of 12.4–136.2 h. The mean temperature for all subjects was 36.93 °C±0.15 °C and 36.96 °C±0.16 °C for the capsule and rectal probe respectively, with no significant difference between the means. The mean difference between readings (capsule–rectal probe) was 0.04 °C±0.03 °C. There was a significant correlation between the capsule and rectal probe temperatures, R 2 = 0.80 , p < 0.05 and R 2 = 0.90 , p < 0.05 for all data points and quiescent periods respectively. Of the average 2916±2132 data points per subject, there was a significant ( p < 0.05 ) difference in data points lost, 105±120 with VitalSense vs. 449±697 with the rectal probe. The percentage of missing data points was 3.1%±2.5% for the capsule (monitor out of the one-meter range of the capsule) and 11.4%±15.9% for the rectal probe (primarily due to probe slippage, but also due to removal for personal hygiene). The data support the finding that the VitalSense core body temperature monitoring system is at least as accurate as rectal probe monitors and the subjects found it to be much more acceptable.

Acute mild hypothermia caused by a low dose of X-irradiation induces a protective effect against mid-lethal doses of X-rays, and a low level concentration of ozone may act as a radiomimetic.

Acute changes in core body temperature following exposure to a low dose of X-rays were assessed in unanaesthetized and unrestrained mice. Radiotelemetry techniques were used to monitor core body temperature continuously. Following exposure to a 20 cGy dose of X-rays, the mice displayed a rapid and significant reduction in core body temperature relative to the sham-treated (non-irradiated) control animals. The present studies, and those by others, showed that pre-exposure to X-rays at doses as low as 20 cGy may result in a reduced mortality rate following subsequent exposure to X-rays at mid-lethal dose levels. This indicates an increased tolerance to radiation. An additional experiment was conducted to examine whether the reduction in the mortality rate following exposure to mid-lethal doses of radiation could be found when mice were subjected to a stressor, ozone inhalation, which induced a suppression in body temperature. The results showed that following inhalation of ozone at a concentration of 0.5 ppm, 93% of the treated animals survived a mid-lethal dose of radiation, whereas 50% of the sham-control animals died within 30 days. These results suggest that low-dose-induced tolerance to radiation may be dependent on a brief exposure to ozone, and a reduction in core temperature may be necessary to obtain tolerance effects in response to a mid-lethal dose of radiation.

Continuous measurement of core body temperature in preterm infants.

We tested a transcutaneous core temperature sensor using a method that relies on the principle of zero heat flow. We tested the hypothesis that transcutaneous and rectal temperatures would track within 0.3 degrees C of each other for >90% of the time. A thermistor was placed between the infant's abdomen or back and the incubator's or radiant warmer's mattress, or within the axilla, attached to the skin with a foam adhesive disk insulator. Thirty preterm infants were either placed on their abdomens or backs in a convective incubator or under a radiant warmer, and continuous transcutaneous and rectal temperatures were measured for 1 hour. There were no significant differences between abdominal and core temperatures or between axillary and core temperatures measured in double-walled convective incubators or in radiant warmers. The rectal-abdominal temperature difference was significantly less than the rectal-axillary difference (p < 0.02) in convective incubators, but not when the infant was placed prone under radiant warmers (p = 0.27). Transcutaneous thermometry is reliable for monitoring core body temperature as indicated by rectal temperature in stable preterm infants in a convective incubator.

Determination of striatal extracellular γ-aminobutyric acid in non-hibernating and hibernating Arctic ground squirrels using quantitative microdialysis

This study determined extracellular concentrations of γ-aminobutyric acid ([GABA] ecf) in striatum of non-hibernating and hibernating arctic ground squirrels to test the hypothesis that an increase in [GABA] ecf was associated with profound CNS depression during hibernation. Quantitative microdialysis procedures were employed to circumvent the effects of low temperature on the relative recovery of the analyte across the dialysis membrane and yielded for the first time quantitative in vivo estimates of [GABA] ecf in any brain region or any species. Laboratory housed, wild caught Arctic ground squirrels ( Spermophilus parryii) were implanted intraperitoneally with radio transmitters that enabled the telemetric monitoring of activity and core body temperature ( T b) and bilaterally implanted with cranial guide tubes that enabled the implantation of microdialysis probes into the striatum. Striatal [GABA] ecf was determined in unrestrained, non-hibernating ground squirrels ( T b range 34.7–38.9°C) and hibernating ground squirrels ( T b range 2.9–3.9°C) using extrapolation to zero flow and very slow flow microdialysis techniques. The results show that [GABA] ecf in non-hibernating squirrels was 73 nM and this level was decreased by approximately 50% during hibernation thereby suggesting that an increase in [GABA] ecf does not play a major role in CNS depression during hibernation. The reduction of [GABA] ecf parallels a decrease in plasma and CSF [glucose] and may be related to a decrease in GABA synthesis or reduced voltage dependent release. This paper demonstrates that measurement of extracellular concentrations of neurotransmitters in animals with vastly different body temperatures is possible using microdialysis techniques of extrapolation to zero flow or very slow flow rates that enable 100% recovery. Such quantitative techniques may prove valuable in the study of the neurochemistry of the cerebral mechanisms of hibernation and tolerance to cerebral ischemia exhibited by hibernating animals.

A single dose model of methamphetamine-induced neurotoxicity in rats: effects on neostriatal monoamines and glial fibrillary acidic protein

The neurotoxic effects of a single administration of methamphetamine (MA) were studied under conditions conducive to MA-induced hyperthermia. After a single dose of MA (10, 20, 30, or 40 mg/kg, s.c.) or saline (3 ml/kg) to Sprague–Dawley CD rats, rectal temperatures were monitored for 9 h in a room with an ambient temperature of 22.0±0.5°C. MA induced significant dose-dependent hyperthermia, however, no significant increase in mortality occurred. Neostriatal DA, 5-HT, TH, and GFAP were assayed 3 days following treatment. MA induced dose-dependent reductions of DA, 5-HT and TH, and increased GFAP. For DA, at doses of 20, 30, or 40 mg/kg the reductions were to 71%, 49%, and 29%, and for 5-HT were to 73%, 44%, and 19% of control values. No reductions were seen after the 10 mg/kg dose. Semiquantitative analysis Western blots of TH and GFAP demonstrated that TH was reduced to 52%, 75%, and 28%, and GFAP was increased to 125%, 134%, and 149% of control values at MA doses of 20, 30, or 40 mg/kg, respectively. No significant changes in TH or GFAP were seen at the 10 mg/kg MA dose. These results demonstrate that a single-dose of MA can be as effective as the widely used four-dose every 2 h regimen. Moreover, mortality can be minimized by monitoring core body temperature and preventing MA-induced hyperthermia from exceeding 41.5°C.

Circadian Rhythm Estimation by Core Body Temperature Filtered with Simultaneously Recorded Physiological Data

In field measurements, monitoring of core body temperature is influenced by physical activities; therefore, the estimation of circadian rhythm from the data may not be exact. The purpose of this study is to design a core body temperature filter in order to reduce artifacts induced by physical activities using simultaneously recorded physiological data such as heart rate data. The effects of physical activities on core body temperature and heart rate are assessed through three experiments. Based on the above knowledge, a core body temperature filter was designed. The filter removes part of rectal temperature data as artifact when heart rate rises above a predetermined threshold. As a result, most of the spike-like noise was removed and the filtered temperature data showed sinusoidal variation more than the unfiltered data. The mesor of the estimated rhythm significantly decreased. This filtering method can provide more precise information about circadian rhythm, especially in field measurements.

Pavlovian conditioning of morphine hyperthermia: assessment of interstimulus interval and CS-US overlap.

The present study examined the effect of interstimulus interval on acquisition of conditioned thermal responses produced by trials in which a light/noise stimulus (CS) was repeatedly paired with infusion of morphine sulphate (US). Rats were implanted with a chronic intravenous catheter for drug delivery and a biotelemetry device for remote monitoring of core body temperature. In experiment 1, different groups received morphine either 0.5 (group P0.5) or 15 min (group P15) after onset of the 15-min CS. A third group was exposed to an identical number of CS and US presentations but in an explicitly unpaired manner (group UP). After repeated exposure to morphine, all groups showed a more rapid rise in body temperature in response to drug infusion. Test presentations of CS alone revealed conditioned hyperthermic responses to CS in groups P0.5 and P15. However, the response of the P15 group was smaller than that of the P0.5 group, suggesting weaker conditioning at the longer interstimulus interval. The contribution of CS-US overlap to the diminished associative strength observed in the P15 group was assessed in experiment 2. Groups P0.5/15 and P0.5/30 received infusions of morphine 0.5 min after onset of a 15- or 30-min CS, respectively. Group P15/30 received morphine 15 min after onset of a 30 min CS, whereas group UP/30 received explicitly unpaired presentations of the US and a 30-min CS. Enhancement of the hyperthermic effect of morphine was observed in all groups after ten conditioning trials. Test presentations of the CS without drug revealed that all paired groups had acquired conditioned hyperthermic responses. These results support the conclusion that drug-induced conditioning can occur at relatively long interstimulus intervals when there is sufficient temporal overlap between the CS and unconditioned response evoked by the drug US.

Ozone toxicity in the mouse: comparison and modeling of responses in susceptible and resistant strains.

Previous studies from this laboratory have demonstrated a concentration-related hypothermia and increases in bronchoalveolar lavage (BAL) fluid indexes of toxicity in the rat after exposure to environmentally relevant levels of ozone (O3). In similar studies with C57BL/6J (B6) and C3H/HeJ (C3) mice, other investigators have reported differential effects on BAL toxicity indexes between the two strains after O3 exposure. The present study investigated the relationship between the reported strain differences in BAL parameters in B6 and C3 mice exposed to O3 and the induced hypothermic response. Male 80-day-old mice (n = 94, 47/strain) were used for these studies. Subsets (n = 8/strain) of these animals were surgically implanted with radiotelemetry transmitters that permitted continuous monitoring of core body temperature and activity. All telemetry animals and an equal number of nontelemetry animals (n = 8/strain) were exposed to filtered air for 24 h followed by a 2-h exposure to 2 parts/million 16O3. With use of a similar protocol, groups of nontelemetry mice (n = 12/strain) were exposed to either filtered air or 2 parts/million 16O3 for 2 h. At 0 or 22 h postexposure, mice were anesthetized with halothane and intubated, and their lungs were lavaged with 37 degrees C saline. Although both strains of mice exhibited significant abrupt decreases in core body temperature on exposure to O3 and both recovered rapidly after cessation of the O3 exposure, the response of the C3 mice was more dynamic than that of the B6 mice. Similarly, both strains showed characteristic changes in biomarkers of O3 toxicity; however, the increases in BAL fluid protein and cells at 22 h postexposure were significantly greater and the percentage of neutrophils was significantly less in B6 mice than in C3 mice. It is possible that the strain differences in BAL constituents may be related to the differences in the hypothermic response.

Role of the suprachiasmatic nuclei in the circadian timing system of the squirrel monkey. II. Light-dark cycle entrainment

The role of the suprachiasmatic nuclei (SCN) in light-dark (LD) cycle entrainment in the squirrel monkey (itSaimiri sciureus) was evaluated by continuously monitoring core body temperature and drinking behavior in both intact and SCN-lesioned animals exposed to different LD conditions. In a 24-h LD cycle with 12 h of light per day (LD 12:12), both intact and SCN-lesioned monkeys had a prominent rhythm in body temperature with an acrophase 6.51 ± 0.36h (SCN-lesioned) after light onset. In a 23-h LD cycle composed of 1 hr of light and 22 h of dark (LD 1:22), the temperature rhythm in both intact and SCN-lesioned monkeys became synchronized with the 23-h period of the LD cycle. Studies examining the effects of LD cycle exposure on the temporal pattern of drinking behavior indicated that both intact and SCN-lesioned monkeys confined their drinking to the daily period of light. Each monkey was subsequently exposed to an LD cycle with 6 h of bright light and 18 h of darkness or dim background illumination (i.e. 60:0, 66:6 and 76:16 lux cycles). In intact monkeys systematic increases in the average intensity of the daily LD cycle produced corresponding delays in the phase of the daily offset of drinking behavior but did not alter the basic 24-h rhythmicity in the behavior. In contrast, increasing the intensity of the 24-h LD cycle in SCN-lesioned monkeys produced no delay in the daily termination of drinking, but instead produced a disintegration in the 24-h rhythm of drinking behavior. These data indicate that 24-h drinking rhythms in SCN-lesioned monkeys housed under LD cycles are not generated by the circadian system but are the result of a ‘masking’ effect of the LD cycle on drinking behavior. These studies demonstrate that the SCN play a fundamental role in LD cycle entrainment of circadian drinking behavior but are not required for LD cycle entrainment of the circadian rhythm of core body temperature, or the mediation of the masking effects of LD cycles on drinking behavior.

Urinary bladder temperature monitoring: a new index of body core temperature.

A new method of core body temperature monitoring is introduced and compared to currently used methods. A close correlation exists between urinary bladder temperatures and each of the techniques studied. The correlation is good when compared to esophageal and rectal temperature and best when compared to pulmonary arterial blood temperature. During rapid rewarming after extracorporeal circulation, the urine temperature consistently increases faster than rectal or esophageal and seemingly is a better measure of blood temperature rather than muscle mass temperature. Urine temperature monitoring is reliable, safe, convenient, and accurate for routine intraoperative and postoperative continuous use in adult patients with urethral catheterization.