Effect of thermal history on the rat's response to varying environmental temperature.

After acclimating individually housed male rats to temperatures of either 24.5 +/- 0.1 or 29.2 +/- 0.1 degrees C for 14 days, randomly paired animals from each group were acutely exposed (3 h) in series to experimental temperatures between 18.0 and 34.5 degrees C in a controlled environment room. Relative humidity of 50 +/- 0.3% and a 12-h light-dark photoperiod (light from 0900 to 2100 h) were maintained. Metabolic rate (MR) and evaporative water loss (EWL) were-measured using an open-flow system; thermistors were used to measure the rectal (Tre) and tail skin (Tts) temperatures. MR was relatively constant over a temperature range of 22.2 to 27.0 degrees C for rats acclimated to 24.5 degrees C and 20.0 to 29.2 degrees C for rats acclimated to 29.2 degrees C. Above and below these ranges, MR for both groups was significantly (P less than 0.05) elevated. At their respective acclimation temperatures, the absolute Tre and Tts of 29.2 degrees C rats were maintained at an elevated level compared with 24.5 degrees C rats. Although EWL for both groups was relatively constant between 18.0 and 27.0 degrees C, 24.5 degrees C rats displayed higher EWL changes at most environmental temperatures above 27.0 degrees C. At 34.5 degrees C, 29.2 degrees C rats dissipated 26% more metabolic heat by evaporation compared with 24.5 degrees C rats. These data suggest that acclimation temperatures of rats affected the thermoneutral zone and alter the set-point temperature around which thermal responses are regulated.

Acclimation of rats following stepwise or direct exposure to heat.

The physiological changes in male rats during acclimation were studied following direct or stepwise exposure to heat (32.5 degrees C) in a controlled-environment room. The animals were exposed to each temperature for 10 days beginning at 24.5 degrees C and returning to 24.5 degrees C in the reverse order of initial exposure. Relative humidity of 50 +/- 2% and a 12-h light-dark photoperiod (light from 0900 to 2100 h) were maintained. Physiological changes in metabolic rate (MR), evaporative water loss (EWL), plasma corticosterone, body water turnover, and food and water intake were measured. The results indicate a significantly (P less than 0.001) elevated plasma corticosterone and MR in rats exposed directly to heat from control temperature (24.5 degrees C) but not in those animals exposed stepwise via 29.0 degrees C. All kinetic parameters of water pool changed (P less than 0.01) on direct exposure to heat, whereas rats exposed in a stepwise manner increased only pool turnover. In addition, exposure to experimental temperatures resulted in reduced (P less than 0.05) relative food intake and increased (P less than 0.05) water intake. Compared with the control condition of 24.5 degrees C, EWL was significantly (P less than 0.05) elevated when the animals were exposed either directly or in a stepwise fashion to 32.5 degrees C. These data suggest that the response to elevated temperatures is influenced by the temperature to which the rat is acclimated.

Effect of hypoxia and hyperoxia on human +Gz duration tolerance.

To determine the effects of varying inspired O2 on positive radial acceleration (+Gz; i.e., head-to-foot inertial load) duration tolerance, seven men were exposed to the +4.5- to +7.0-Gz simulated aerial combat maneuver (SACM) by use of the Armstrong Laboratory (Brooks Air Force Base) centrifuge. Exposures were repeated on different days while subjects breathed gas mixtures of fractional concentration of O2 in inspired air (FIO2) between 0.12 and 0.6. SACM duration tolerance was positively related to inspired O2 of FIO2 between 0.12 and 0.2 but was unchanged at FIO2 between 0.2 and 0.6. SACM exposure decreased arterial O2 saturation and increased heart rates; SACM-induced changes were additive to FIO2 effects. The positive relationship between blood lactate and SACM duration tolerance at all FIO2 indicated an anaerobic component. It is concluded that SACM duration tolerance is limited by reduced FIO2 but not enhanced by hyperoxia. Thus the aerobic component of +4.5- to +7.0-Gz SACM duration tolerance is much greater than previously believed.

The role of psychological factors in the report of building-related symptoms in sick building syndrome.

Sick building syndrome (SBS) is an increasingly common problem, although continued skepticism exists regarding its validity. Because of this, the attribution of complaints to psychogenic causes or mas hysteria persists. In this study (N = 111), self-report measures of psychopathology (Minnesota Multiphasic Personality Inventory [Hathaway & McKinley, 1983] and SCL-90-R [Derogatis, 1983]) and physical symptom reports failed to discriminate symptomatic from nonsymptomatic workers in an affected building but could more generally differentiate workers in the target building from control subjects. These results suggest that SBS cannot be justifiably attributed to psychological factors alone, although working in a contaminated environment appeared to have deleterious psychological consequences for some workers. Smoking history (in pack/years [packs per day x number of years smoked]) was reliably associated with the development of symptoms in exposed workers. Issues related to the assessment of psychological complaints in SBS are discussed.

Altered hypothalamic dopamine depletion rate and LHRH content in noncyclic hamsters.

Effect of light deprivation on hypothalamic dopamine (DA) depletion rate and luteinizing hormone releasing hormone (LHRH) content was evaluated in golden hamsters. Hamsters maintained in continuous darkness (CD) became acyclic after about 6 weeks while another group of hamsters maintained vaginal cyclicity under 20 lux light intensity for 14 hours a day. All hamsters were ovariectomized subsequently. Luteinizing hormone releasing hormone levels were significantly higher in the medial basal hypothalamus (MBH) and the serum gonadotropin levels were significantly lower in CD hamsters when compared with 20 lux group. However, gonadotropin release in response to exogenous LHRH was not significantly different in CD or 20 lux group of hamsters. Examination of hypothalamic catecholamine levels one hour after alpha-methyl-p-tyrosine injection indicated that the DA depletion was higher in CD animals. Results indicate that light deprivation probably enhances DA depletion rate in the MBH, suggesting that increased activity in dopaminergic neurons may inhibit the release of MBH LHRH in hamsters kept in continuous darkness.

A simple remote-controlled power switch for internalized bioelectronic instrumentation.

This communication presents a remote-controlled power switch for extending the battery life of biomedical instruments implanted into animals or humans. The switching action is controlled externally to the implant by an inductive link between two coils, one contained in the implant and one external to the implant. The external coil sends an electromagnetic pulse to the implant, triggering a CMOS "D" flip-flop connected as a toggle switch--its state is toggled on or off upon receiving the external pulse. The standby current drain of the switch is about 4 nA. The remote triggering range is approximately 20-50 cm. Testing of the switch, surgically implanted as part of a telemetry transmitter, is also discussed.

Technical note: a noninvasive procedure for measuring goat heart rates.

Heart rates were obtained simultaneously from FM radio transmitters and heart rate monitors externally mounted on unanesthetized and unrestrained mixed-breed goats. Data from transmitters were highly correlated (r = .92, P < .0001) with data from monitors and the percentage difference in heart rates between the two devices was less than that observed between animals. Analyses also revealed that radio transmitters provided a reliable, repeatable, and valid method for the noninvasive measurement of goat heart rates.

Telemetry measured body temperature of domestic fowl at various ambient temperatures.

Adult, male Single Comb White Leghorn chickens (SCWL) were housed unrestrained in individual cages in a controlled environment room with a photoperiod of 12L:12D. By means of surgically implanted radio transmitter, body temperatures were recorded hourly for five consecutive days at each of six experimental temperatures: 23, 26, 29, 32, 35, and 38 C. The data were evaluated statistically by correlogram, periodogram, and harmonic analysis. Period length of each cycle was about 24 hr at all ambient temperatures. No significant differences in deep body temperature were observed until the ambient temperature reached 32 C; but highly significant increases were detected between 32, 35, and 38 C. Diurnal differences in body temperature ranged from .6 to 1.1 C. It has been suggested that the body temperature of male chicken may be under the control of a biological clock that synchronizes with the solar day.

Feeding time and body temperature interactions in broiler breeders.

Four groups of 70-wk-old broiler breeder females were fed once daily at 0600, 1000, 1400, and 1800 h to determine the effect of feeding time and eating on body temperature. The photoperiod was from 0430 to 1930 h. Four floor pens of 30 hens each were assigned per feeding time. Following a 9-day adjustment period, body temperature was determined, in series, by rectal probe of 5 birds/pen at 7 and 3 h prefeeding and 1, 5, 9, and 13 h postfeeding. Body temperature was increased .5 C at 1 h postfeeding in all groups and at 5 h postfeeding in the 0600-h fed group. The rate of feed consumption was fastest with afternoon feeding. Four 1-yr-old broiler breeder males were implanted with an FM radio transmitter for monitoring body temperature and housed in an environmental control chamber. Body temperature was monitored when the birds were fed at 0600, 1000, 1400, and 1800 h. The chamber temperature cycled from 22.2 to 33.3 C (22.2 C: 2200 to 0800 h; 33.3 C: 1200 to 1600 h; 27.8 C: 0800 to 1200 h and 1600 to 2200 h). Lights were on from 0430 to 1930 h. Body temperature changes were also monitored under constant temperature (27.8 C) and light for birds fed ad libitum or at 1000 h. Body temperature increased as much as 1.5 C following feeding and reached a maximum at 5, 4, 3, and 2 h postfeeding at feeding times of 0600, 1000, 1400, and 1800 h, respectively. Males unable to feed displayed a significantly increased body temperature when they observed other birds eating. A specific body temperature response to feeding activity was observed only when males were fed once daily under constant environment.

Environmental quality within animal facilities.

Maintenance of environmental quality for laboratory animals involves more than heat and moisture production of animals or room air changes per hour. Heating, ventilating and air conditioning of animal facilities allows control of room temperature and humidity, cage microenvironment, gaseous and particulate contamination, air distribution and diffusion, air quality and temperature differentials. However, other factors may influence environmental quality: population density, species of animals, and husbandry and sanitation practices. Because of all of these considerations, animal facilities tend to be energy intensive. Recommended environmental conditions are designed to satisfy physiological requirements of animals but prevent physiologic and psychophysiologic stresses. Analytical studies will provide necessary information to attain these goals and simultaneously reduce energy expenditures or minimize the need for expensive control systems.

Regulation and its role in the prevention of building-associated illness.

Many groups have as their common goal the maintenance of acceptable indoor air quality, which protects occupants from adverse health effects and discomfort, but no one group possesses the interest or expertise to deal with all of the IAQ issues. Nonetheless, conclusions can be made regarding available alternatives to mitigate indoor air quality problems, including building-associated illness. It has been suggested that congressional action is needed in three areas related to BAI and IAQ: Recognition that controlling outdoor air only--even if "health based"--will not result in substantial improvement of public health; Definition of responsibilities for achieving healthful indoor environments; and Resolution of jurisdictional disputes between various federal agencies. Through their studies of buildings whose occupants complained of building-associated illness, NIOSH and others have concluded that inadequate supply and distribution of outdoor air to indoor spaces are the most common causes of SBS. Nonetheless, there are no reports of follow-up studies which confirm that the recommended ventilation upgrades actually solved the IAQ problems. Other reports indicate that maintenance, energy management, and air distribution are as important as ventilation rate. Corrective action, therefore, should include these issues. Systematic research directed toward providing cost-effective and innovative solutions should be the driving force. Rather than regulation, governments should assist in funding the necessary research, providing educational, technical and legal assistance, and developing policy options directed at reducing indoor air pollutants. In those cases where the specific causes of IAQ problems can be identified, remedial actions should be immediately implemented utilizing available technology. It has been suggested that "sick buildings" resulted from too much emphasis on efficency and safety and not enough on occupant health and well-being. Because health has been defined as "a state of complete physical, mental and social well-being not merely the absence of disease or infirmity," greater emphasis should be given to the concept of control and maintenance of healthy indoor environments (i.e., "healthy buildings") through utilization of quality assurance measures. Also, human response, system performance, and service factors should be utilized to assure an acceptable building performance. Finally, building designers, contractors, owners, managers, and operators must be knowledgeable regarding indoor air quality problems and their consequences and work together to build and maintain healthy buildings. This includes developing training, education, monitoring, and preventive maintenance programs to assure accountability for the proper management of the building systems. The certification (or licensing) of those responsible for providing indoor air quality has been suggested.

Adrenal and body temperature changes in rabbits exposed to varying effective temperatures.

Eight adult New Zealand White rabbits were exposed individually, in series, to each of 23 effective temperatures (t(eff)) until body temperature (tb) increased 1.1 degrees C or for a period of 2 hours. Body temperature was measured to the nearest 0.1 degree C using FM radio transmitters in the pre-test (baseline) condition and at 2 minute intervals during the test conditions where t(eff) ranged between 21.7 and 34.7 degrees C. The frequency at which the rabbits displayed a 1.1 degree C rise in tb was related to the magnitude of the t(eff), with 100% of the rabbits manifesting this change at t(eff) greater than 30.2 degrees C. At t(eff) of 28.4 through 30.2 degrees C, some, but not all, of the rabbits showed a 1.1 degree C rise in tb whereas none displayed the 1.1 degree C rise in tb at t(eff) below 28.4 degrees C. The mean time necessary for the 1.1 degree C rise in tb was negatively correlated (P less than 0.01) to the magnitude of the t(eff). The significantly (P less than 0.01) elevated plasma corticosterone in rabbits exhibiting 0.6 degree C and 1.1 degree C rise in tb suggests that those animals were stressed physiologically by the experimental procedure. It is concluded that the conditions associated with increased tb induce physiological changes commonly associated with stressors and that the techniques reported herein should be useful in establishing upper environmental temperature limits for housing rabbits.

Estrous cycle variations of food and water intake in rats in the heat.

Effects of heat and estrous cycle on food and water intake and on the kinetics of water metabolism were studied in Holtzmann rats, 12 adult females per group. The animals were housed individually in metabolic cages, in series, in a controlled-environment room at (24.5 degrees C) followed by two experimental temperatures (29.2 degrees C and 34.0 degrees C). In all cases relative humidity was 50% and the photoperiod 12L:12D (L = 0600--1800 h). Intake of food and water, available ad libitum, were measured and recorded daily for at least five consecutive estrous cycle (about 25 days). Water turnover was measured using tritiated water. The results indicate that the experimental conditions constituted stressful environments for the rats. Their corticosterone levels were significantly (P less than 0.01) elevated and a relative lymphopenia and neutrophilia (P less than 0.01) were observed. Additionally, food intake was decreased and water intake increased, both significantly (P less than 0.01). Body water turnover was increased (P less than 0.01) while body water pool size and the biological half-life for 3H2O were reduced. However, the cyclic variation of food and water intake and its relationhsip to the estrous cycle were unchanged.

Heat dissipation biorhythms of laboratory animals.

Body heat dissipation rates were determined in greyhound and beagle dogs, the rabbit, and the rat. Each group of animals was confined in standard cages in a controlled environment room maintained under conditions of 24 degrees C, 50% relative humidity, and fixed ventilation rats. Food and water were available ad libitum. Heat dissipation rates were determined for each group and normalized to an individual animal basis. The ratio of actual heat dissipation to standard metabolic rate, the metabolic heat ratio, was 2.01+/-0.18 for the greyhound, 1.98+/-0.03 for the beagle, 2.66+/-0.20 for the rabbit, and 1.95+/-0.13 for the rat. For each species, the ratio displayed a 24-hour cyclic pattern in which four contiguous maximum values differed significantly from four contiguous minimum values. The ratios of maximum values to minimum values were between 1.54 and 1.75.

Adrenal and thyroid interactions of beta-endorphin-induced body temperature responses of rats at 24.5 degrees C.

The effect of beta-endorphin (beta-END) and the role of the adrenal and thyroid glands on body temperature were examined in male rats in a controlled environment room at 24.5 +/- 0.1 degrees C. Relative humidity of 50 +/- 0.3% and a 12L:12D photoperiod (L = 0900 to 2100 hr) were maintained. Rectal temperature (Tr) was measured using thermistors. Corticosterone and thyroid hormones were determined by radioimmunoassay. Intracerebroventricular (IVT) administration of varying doses (0.05 to 50.0 micrograms) of beta-END resulted in a hyperthermia that began 30 min post-IVT injection and continued for an additional hour. Intravenous injections of the same doses of beta-END resulted in little or no Tr response. The beta-END-induced hyperthermia was antagonized by intraperitoneal injection of naloxone. Pretreatment with propranolol, phenotolamine, or both drugs in combination did not block the hyperthermia caused by beta-END. Adrenalectomized or hypophysectomized rats receiving IVT injections of beta-END did not consistently display an increased Tr. beta-Endorphin administration had no detectable effect on serum corticosterone or thyroxine but serum triiodothyronine was decreased. These data suggest the acute hyperthermic action of beta-END is mediated centrally through opiate receptors and does not involve adrenergic receptors.

Comparative responses of rabbits and rats to elevated noise.

New Zealand white rabbits and Wistar rats were exposed, in an acoustic chamber, to 1.5 hours of white noise per day at intensities of 107--112 decibels. Compared to the control condition of 60 decibels (background noise level), both rabbits and rats displayed increased adrenal weights (p less than 0.05). Rabbits also had decreased spleen and thymus weights (p less than 0.05). Rats had increased total leukocyte counts and a relative eosinopenia (p less than 0.05). Also, noise exposed rats exhibited a decrease (p less than 0.05) in food intake by the third day of noise exposure. There were no observed changes in hematocrit or plasma protein concentrations.