Circadian rhythms of rat internal temperatures and thermal ambiance (author's transl)]

Chronic recording of cerebellar and subcutaneous temperatures were carried out in rats maintained at different ambient temperatures in a 12 h light-dark cycle (light from 7 to 19 h). Cerebellar and subcutaneous temperatures followed a rhythm with a period of 24 h with acrophase at 1 h and an amplitude of 0.75 degrees C. The amplitude and acrophase were not altered by modification of the ambient temperature (20-25-30-34 or 35 degrees C), but each elevation of ambient temperature produced a rise in the mean internal temperature of the rat. This rise, hardly perceptible at ambient temperatures of 25 and 30 degrees C, reaches 0.5 degrees C between 20 and 25 degrees C and 1 degrees C between 30 and 34 degrees C. This elevation of temperature was maintained for the duration of the 10 days of observation. These results pose at least three questions: the degree of liaison between the rhythms of activity (waking) and temperature; the lability of the mean internal temperature, which alter with ambient temperature while the amplitude of the circadian rhythm is unaltered and the absence of reduction of mean interanl temperature several days exposure to a raised ambient temperature, even when activity and metabolism are reduced by the second day of exposure.     

Effects of ambient temperature on broiler mineral balance partitioned into urinary and faecal loss

1. Two experiments were conducted on control (intact) and colostomised 4 to 7 week old broilers to evaluate the influence of 24 degrees C, diurnally cycling 24 to 35 degrees C and chronic 35 degrees C ambient temperatures on broiler mineral balance, urinary and faecal mineral excretion and urinary osmolar characteristics. 2. In the first experiment, colostomy had no significant effect on mineral balance. However, broilers exposed to high cycling ambient temperature reduced their retention of phosphorus, potassium, sodium, magnesium, sulphur, manganese, copper and zinc compared with birds housed at 24 degrees C. 3. Despite the minimal effect of high ambient temperature on urine production, minerals excreted disproportionately excreted in urine included potassium, magnesium, phosphorus and sulphur while copper and magnesium were lost primarily via the faeces. 4. In the second experiment, exposure to 35 degrees C increased urine output from 50.7 ml/12 h per kg of body weight at 24 degrees C to 101.3 ml/12 h per kg of body weight and was associated with an increased urine:water ratio and reduced urine osmolality. 5. Reduced urinary chloride and higher potassium, phosphorus, sulphur, sodium, magnesium, calcium and manganese excretion was observed for broilers housed in under high ambient temperatures compared to 24 degrees C. 6. These studies suggest that high ambient temperatures adversely influence mineral metabolism and, furthermore, that the route of excretion varies with the specific mineral and the environmental temperature exposure.     

Ethanol anapyrexia in rats

In the present series of experiments we tested whether ethanol decreases body temperature by impairing thermal regulation (poikilothermia) or by shifting the set point downwards. The central temperature of rats kept in a thermocline and the selected ambient temperature were recorded by telemetry. After an IP injection of 2 g/kg of ethanol the rats selected an ambient temperature 7 degrees C lower than the one they selected before the ethanol injection and 8 degrees C lower than the one selected by the same rats after saline injection. At the same time the central temperature decreased by 2.5 degrees C. After about 40 min the rats preferred warmer ambient temperatures and 10 min later the central temperature began to rise. When, after ethanol, the rats were kept at 30 degrees C the central temperature remained at the normal level. At 35-36 degrees C the central temperature of normal rats without ethanol rose, in 1 h, from 37 degrees C to 39.75 degrees C. The results suggest that ethanol hypothermia is due to a downward shift of the set point and, in fact, is an anapyrexia, a condition inverse to fever.     

Identification of murine p120 isoforms and heterogeneous expression of p120cas isoforms in human tumor cell lines

Heat stress is a common problem for cattle. General consequences of heat stress include increased body temperatures and reduced feed intakes. As a measure of heat stress, core body temperatures of unshaded feedlot steers (crossbred Bos taurus) were monitored from mid-June to early November in Nebraska using transmitters implanted in the peritoneum of 10 steers (initially 10 mo of age). Steers were fed at 0630 and 1430 using a finishing diet of 1.52 NEg Mcal/kg with 13% protein and 4% roughage per day and housed in two open lots with stocking densities of 15.2 or 19.3 m2/steer. Core body temperatures, ambient temperature, relative humidity, and wind speed were measured at 3-min intervals and mathematically filtered to produce 120 readings/ d. For 94 usable daily records, body temperature means (39.04 +/- .12 degrees C), maxima (39.89 +/- .21 degrees C at 1836 +/- .73 h), minima (38.33 +/- .29 degrees C at 0823 +/- .38 h), and patterns were similar among steers. As daily maximum ambient temperatures increased, minimum body temperatures decreased slightly (.04 degree C per 5 degrees C; P < .01). After daily maximum ambient temperatures reached a threshold of 25.6 degrees C, daily maximum body temperatures increased linearly with maximum ambient temperatures (.42 degree C per 5 degrees C; P < .01). Sharp peaks in body temperature were often seen in the late evening (approximately 2200) after ambient temperature had decreased to well below maximum values. These evening peaks occurred on an average of 25% of the days, had amplitudes ranging from .7 to 3.5 degrees C relative to mean daily temperatures and lasted for 1.5 h. From a practical standpoint, we suggest that producers monitor meteorological forecast of peak ambient temperatures and make special efforts, such as spraying animals, when exceptionally hot weather is predicted.     

Malignant melanoma in Europe: changes in mortality rates (1970-90) in European Community countries

We measured metabolic rates (mL O2 h-1, converted to kcal d-1), deep body temperatures (degree C), and skin temperatures (degree C) and calculated whole-animal thermal conductances (mL O2 g-1 h-1 degree C-1) of five 3-yr-old harbor seals (Phoca vitulina concolor) at air temperatures between -20 degrees and 35 degrees C. The mean thermal neutral zone of these seals extended from a lower critical temperature of -12.9 degrees +/- 1.6 degrees C (SD) to an upper critical temperature of 28.6 degrees +/- 1.7 degrees C. Hyperthermia was observed at an ambient air temperature of 35 degrees C. Mean standard metabolic rate was 1,553.6 +/- 168.2 kcal d-1, about 1.2 times the value expected for adult animals of similar body mass (mean mass = 49.2 +/- 7.5 kg). Mean deep body temperature increased from 37.5 degrees +/- 0.30 degrees C at an ambient temperature of 30 degrees C and reached 39.3 degrees +/- 0.33 degrees C at an ambient temperature of 35 degrees C. Skin temperature decreased with decreasing ambient temperature but remained well above ambient temperature. Mean whole-animal thermal conductance decreased from an ambient temperature of 35 degrees C until it reached a minimum value of 0.007 mL O2 g-1 h-1 degree C-1 at -4.0 degrees C; it then increased with a further decrease in ambient temperature. In comparison to the thermal limits of the same seals during their first year of life, the results indicate a broadening of the thermal neutral zone with age: an 11 degrees C decrease in the lower critical temperature and a 3.5 degrees C increase in the upper critical temperature. These findings suggest that warm ambient air temperatures should not pose any particular thermoregulatory problems for larger and older harbor seals, even beyond the limits of their current annual distribution.     

Ultrasound measurement of bone

The importance of photoperiod and ambient temperature on the accumulation of cadmium in the liver and kidneys of bank voles was determined in the present study. Males and females, aged 1 month, were given 3.0 micrograms Cd ml-1 drinking water and divided into four groups according to photoperiod (16 h light/8 h dark and 8 h light/16 h dark) and ambient temperature (20 or 5 degrees C); liver and kidneys were removed for cadmium as well as copper, iron and zinc analyses at the end of 6 weeks. Bank voles exposed to 5 degrees C in both photoperiods consumed approximately 30% less water containing cadmium than those kept at 20 degrees C. However, the total accumulation of cadmium in the liver and kidneys of males and females exposed to the low temperatures was 4.3-4.8 and 2.2-3.3 times less than that in animals maintained at room temperature in the long and short photoperiod, respectively. Simultaneously, the low temperature brought about an increase in the copper concentrations in the liver (12-43%) and kidneys (47-78%), giving rise to an inverse correlation between the cadmium accumulation and the tissue copper concentration. In contrast to cadmium and copper, the concentrations of iron and zinc were affected primarily by photoperiod. These findings indicate that ambient temperature is an important determinant of cadmium retention in the bank vole. It appears that low temperature decreases tissue cadmium accumulation not only by reducing cadmium intake but also through changes in copper metabolism.     

Jackrabbit ears: surface temperatures and vascular responses

Blood flow to the ear pinnae is curtailed at ambient temperatures of between 1.4 degrees and 24 degrees C, which minimizes heat loss across the pinnae and allows the surfaces of erect pinnae to approach ambient temperature. The pinnae are warmed by steady or pulsatile vasodilation in some animals when the ambient temperature is between 1 degree and 9 degrees C below body temperature, a response favoring heat loss. When ambient temperature exceeds body temperature by 4 degrees to 5 degrees C, the pinnae are circulated with blood cooler than ambient temperature; this response favors heat influx.     

Physiological and psychological effects of head heating during rest and work

The purpose of this study is to obtain some knowledge related to physiological and psychological effects of head heating by radiation on the vital body under varying conditions of the environmental temperature and physical activity. The study was proceeded with experiments 1 and 2 using 8 women, all in good health as subjects. In experiment 1, firstly the subject at rest was kept at an ambient temperature of 28 degrees C for 40 minutes. The, moving to a room kept at an ambient temperature of 18 degrees C or 28 degrees C, the state at rest was maintained with head heating at 3 radiant intensities (without radiation, 35 degrees C and 40 degrees C of globe temperature) for a further 40 minutes. In experiment 2, continued from the same procedure of experiment 1, work on the ergometer was performed for 30 minutes with head heating at 2 radiant intensities (without radiation and 35 degrees C of globe temperature). Items measured were tympanic temperature, skin temperatures, heart rate, and subjective sensations. The principal results obtained are as follows: 1) Tympanic temperature, forehead skin temperature and score of thermal sensation of head increased, while the others decreased at 18 degrees C. 2) Decrease of scores was inhibited by head heating in finger skin temperature, toe skin temperature and heart rate. 3) When radiant intensities at 35 degrees C and 40 degrees C were compared, statistical significant difference was noted in forehead skin temperature only, the difference of radiant conditions gives a little effect to the vital body. 4) Effects brought by head heating during rest decreased owing to the addition of work.     

Metabolic responses of White Pekin ducks to ambient temperature

Metabolic responses of unrestrained White Pekin ducks, Anas platyrhynchos, were determined at ambient temperatures of -5 degrees, 1 degrees, 10 degrees, 20 degrees, and 30 degrees C. Temperatures from the pectoralis and the subcutaneous back were monitored. Unrestrained ducks exhibited two metabolic states, a high response (540 cc. O2/kg/hr. at 20 degrees C.) and a low response (427 cc. O2/kg./hr. at 20 degrees C). Pectoralis muscle temperature did not vary greatly over the range of ambient temperatures tested and was considered to be a good representative of body temperature.     

Cost of locomotion and heat balance during rest and running from 0 to 55 degrees C in a patas monkey

A young patas monkey was run on a treadmill for 15-20 min at speeds in excess of 15 km times h-1 over a range of laboratory air temperatures from 0 to 55 degrees C. Cost of locomotion for the monkey was 83% that predicted for a running mammal of similar weight, 4 kg. At the highest steady-state running of speeds, the patas monkey's energy expenditure was 11 times the resting rate. Heat storage and respiratory evaporation during running each accounted for less than 16% of the heat production. Cutaneous evaporation, mainly sweating, was the major means of heat loss at high ambient temperatures and during heavy exercise. Maximum sweat rates of 0.5 mg times cm-2 times min-1 found in these experiments approach the sweat rates of humans. Whole-body dry thermal conductance increased 2-3 times the rest value at a given temperature. Environmentally gained heat contributed about two-thirds of the total heat load on the patas monkey at rest at 53 degrees C. At these same temperatures, environmental and metabolic heat loads were about equal when the animal ran at moderately high speeds (11-13.4 km times h-1).     

Daily wheel running activity modifies the period of free-running rhythm in rats via intergeniculate leaflet

The period of free-running rhythms (tau) in rats, as measured using a running wheel, is different from that measured using an Automex. The aim of this work was to examine the effects of lesions of the intergeniculate leaflet (IGL) on the tau of these two activity rhythms. When blind rats were transferred from a cage with a running wheel to a cage without a running wheel, the tau lengthened. The tau of the wheel-running activity was associated with the number of wheel revolutions per day. A complete lesion of the IGL lengthened the tau of the wheel-running activity, and caused a reduction in the number of wheel revolutions per day in all rats. In rats housed in cages without a running wheel, locomotor activity was reduced by IGL lesions, although the tau was unaffected. When IGL-lesioned rats were transferred from a cage with a running wheel to a cage without a running wheel, no further change was observed. These results indicate that the tau is modified by the daily activity of wheel-running, but not by general locomotor activity, and that the IGL may be involved in this modification.     

The effects of lipopolysaccharide (LPS) on the fever response in rats at different ambient temperatures

There is a complex interplay between the immune system, nervous system, and sleep. When an organism is challenged with lipopolysacchride (LPS), the immune system is stimulated, producing a fever response that is independent of ambient temperature, and an increase in slow-wave sleep (SWS). The study investigated sleep patterns of immune-challenged rats during the light phase cycle to determine the effects of various ambient temperatures. It was hypothesised that fever response would occur independently of ambient temperatures. Also, the febrile response would be monophasic, and there would be an increase in slow-wave sleep (SWS) and a decrease in rapid-eye-movement (REM) sleep. Thirty Wistar rats were randomly placed in 3 different ambient temperature groups, 22 degrees C, 15 degrees C, and 30 degrees C. Within each of these conditions, the same subjects served as control and experimental groups. Four animals were placed in 4 subsections of 2 standard boxes that were placed in the ambient-temperature box. The electrodes were connected to the analog to digital computer board, where all the data was processed and stored on a hard drive. The animals were injected I.P. with saline and recorded for a period of 6 h to establish a baseline. On Day 2, the same animals were injected I.P. with LPS and recorded for 6 h to determine the febrile effects of LPS on the immune system; the same procedure was repeated in the other ambient temperatures. The results have shown that animals experienced a monophasic fever response in low and normal temperatures, but not in the high temperatures. Although there was no increase in SWS, there was a significant decrease in REM sleep in 3 groups.     

Effects of the menstrual cycle on dressing behavior in the cold

The purpose of the present study was to determine the effect of the menstrual cycle on dressing behavior in cold exposure. Rectal and skin temperatures, temperature sensation and metabolic rate were measured in seven women during the luteal (L) and the follicular (F) phases of the menstrual cycle, as was their dressing behavior in these two phases. The subjects were instructed to dress so as to feel comfortable when the ambient temperature was decreased from 30 degrees C to 15 degrees C (07:00-09:00). Most subjects dressed more quickly and with thicker clothing in the L phase. They felt cooler in the L phase during the last 30 min of the temperature fall. Rectal and skin temperatures showed significant differences between L and F phases and metabolic rate was significantly higher in the L phase. The results can be interpreted in terms of the establishment of a higher set-point in core temperature during the L phase.     

Participation of bdellovibrios in sewage self-purification processes

The participation of bacterial parasites belonging to the genus Bdellovibrio in the processes of sewage self-purification was studied in refineries of Pushchino. The lytic activity of Bdellovibrio resulting in a decrease of the number of heterotrophic Gram-negative bacteria and E. coli in sewage was found to depend on the temperature factor influencing the intensity of interaction between the parasite and the host bacterium. The maximal p/h (parasite/host) index was found at the water temperature of 26 degrees C and the minimal one at 19 degrees C. Sewage purified at 26 degrees C and transferred to a precipitation tank contained 800 cells of E. coli in 1 ml while that purified at 19 degrees C contained 4000 cells in 1 ml. The number of interacting organisms varied in sewage which was typical of the "parasite-host" relations. Therefore, Bdellovibrio should be involved in the self-purification of sewage from the intestinal microflora at 26 degrees C; to a lesser extent, at 23.5 degrees C; and not at all, at 19 degrees C.     

Atropine substitutes and the writhing syndrome in mice

Eight subjects underwent an exercise training program (10 days at 75% VO2max for 1 h/day at 25 degrees C db/13 degrees C wb) and a heat-acclimation program (10 days at 50% VO2max for 1 h/day at 35 degrees C db/32 degrees C wb). The relations of chest sweat rate and of forearm blood flow to internal temperature were determined for each subject at a 25 degrees C ambient temperature before training, between training and acclimation, and following acclimation. Training shifted the vasodilation and sweating thresholds toward lower internal temperatures, and acclimation further lowered these thresholds. All threshold shifts were statistically significant (P less than 0.05). Training and acclimation both appeared to increase the slope of the sweating relation, but these effects were not statistically significant. Changes in the slope of the blood flow relation were small and inconsistent. Since arm blood flow is higher at any given internal temperature after acclimation, the lower blood flow which is reported to accompany heat acclimation must result from the lower body temperatures.     

Effects of various ambient temperatures and of heating and cooling the hypothalamus and cervical spinal cord on antidiuretic hormone secretion and urinary osmolality in pigs

1. Plasma ADH concentration, urinary and plasma osmolality and haematocrit were measured in young pigs placed in cold, thermoneutral, warm and hot ambient temperatures. In some experiments a thermode placed in the hypothalamus or over the cervical spinal cord was heated or cooled at various ambient temperatures. 2. Plasma ADH concentration remained at a low level (0-5--5 muu. ml.-1) over 2 hr or 3 hr periods when the pigs were in cold, thermoneutral or warm ambient temperatures. A hot environment, which caused a marked rise in the pigs' rectal temperature, was associated with a large rise in plasma ADH level. 3. The rise in plasma ADH level which occurred during an increase in body temperature was consistently and completely suppressed by simultaneous cooling of the thermode in the pre-optic region to 5 to 10 degrees C. When the thermode was in the region of the supraoptic nucleus the rise in ADH was only partly suppressed, and when it was over the cervical cord it was only sometimes suppressed. 4. Cooling the thermodes in any position at a cold or thermoneutral ambient temperature, or heating them at a thermoneutral or warm ambient temperature, caused no consistent change in ADH. 5. A diuresis, with a urinary flow-rate of at most 1 ml. min-1 and minimal urinary osmolality of 53 m-osmole kg-1, was observed on only three occasions, twice during cooling of a thermode in the hypothalamus and once after the end of a period when the thermode was heated. In each case, the plasma ADH was less than 2 muu. ml.-1. 6. A slight rise of haematocrit in cold ambient conditions and a slight fall in the warm were observed. Otherwise changes in haematocrit were trivial, and a shift of water between vascular system and interstitium could not be invoked to account for changes in ADH levels. Observed variation of plasma osmolality was also slight.     

A method for determination of thermally motivated behavior (author's transl)

Constant body temperature in homeothermic organisms results from autonomic and behavioral thermoregulatory reactions. The input variables for thermally motivated behavior are temperatures of the skin and of the hypothalamus. Our aim was to determine the behavioral side of thermoregulatory reactions under the influence of drugs interfering with normal body temperature. Initial experiments were made with phentolamine, which at an ambient temperature of + 4 degrees C causes a dose dependent hypothermia. Rats were trained in a cold box to press a lever and were rewarded by a certain amount of warm air. Trained rats were able to raise the temperature in the box from -4 degrees C up to + 4 degrees C at a response rate of 0.5 min. Treated with phentolamine (3.7-15 mg/kg) these rats increased the rate of lever pressing dose dependently, i.e. they increased their ambient temperature. The hypothermic effect of the drug was therby reduced to a certain extent. Using this method it can be determined whether a drug influences body temperature at the level of autonomic reactions or at that of thermally motivated behavior or at those of both.     

Thermal Stability of <Emphasis Type="Italic">α</Emphasis> Phase of Titanium by Using X-Ray Diffraction

At room temperature and ambient pressure, crystalline titanium has a hexagonal-close-packed (hcp) lattice and at high temperature appears as a body-centered-cubic (bcc) structure. In fact, the phase transitions of titanium have been investigated under various pressures and temperatures. However, the phase transitions of titanium have been mostly reported at high pressure, while less attention has been paid to various ranges of high temperature. Therefore, in this study, we have considered the thermal stability of α phase of titanium by using X-ray diffraction (XRD) at high temperature. The observed experimental results of the diffraction show that the stability range of α phase varies between room temperature to around 923 K (650 °C).     

Small changes in ambient temperature cause large changes in 3,4-methylenedioxymethamphetamine (MDMA)-induced serotonin neurotoxicity and core body temperature in the rat

The amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA) is a drug of abuse and has been shown to be neurotoxic to 5-HT terminals in many species. MDMA-engendered neurotoxicity has been shown to be affected by both ambient temperature and core body temperature. We now report that small (2 degreesC) changes in ambient temperature produce changes in core temperature in MDMA-treated rats, but the same changes in ambient temperature do not affect core temperature of saline-treated animals. Furthermore, increases in core temperature of MDMA-treated animals increase neurotoxicity. Rats were given MDMA (20 or 40 mg/kg) or saline and placed in an ambient temperature of 20, 22, 24, 26, 28, or 30 degreesC using a novel temperature measurement apparatus that controls ambient temperature +/-0.5 degrees C. Two weeks after MDMA treatment, the rats were killed, and regional 5-HT and 5-hydroxyindole acetic acid levels were analyzed as a measure of neurotoxicity. Rats treated with MDMA at 20 and 22 degrees C showed a hypothermic core temperature response. Treatment with MDMA at 28 and 30 degreesC produced a hyperthermic response. At ambient temperatures of 20-24 degrees C, neurotoxicity was not observed in the frontal cortex, somatosensory cortex, hippocampus, or striatum. At ambient temperatures of 26-30 degrees C, neurotoxicity was seen and correlated with core temperature in all regions examined. These data indicate that ambient temperature has a significant affect on MDMA neurotoxicity, core temperature, and thermoregulation in rats. This finding has implications on both the temperature dependence of the mechanism of MDMA neurotoxicity and human use because fatal hyperthermia is associated with MDMA use in humans.     

Hemophagocytic syndrome: an underestimated cause of the syndrome of non-infectious fever?]

The effects of two ethanol doses (2 and 3 g/kg) on colonic temperature and levels of norepinephrine (NE) and uncoupling protein (UCP) mRNA in the interscapular brown adipose tissue (IBAT) were examined in rats exposed to 20 degrees C or 4 degrees C for 2 h. The controls received 0.9% NaCl solution. Ethanol produced a significant hypothermic effect versus saline at both temperature conditions. The dose at 3 g/kg reduced colonic temperature more in the cold than at room temperature (p < 0.01), whereas the ambient temperature did not affect the decrease in rats that received ethanol 2 g/kg. At room temperature ethanol did not significantly change the levels of NE or UCP mRNA, whereas after cold exposure (4 degrees C) NE levels in the ethanol-treated rats were significantly lower than in the controls (p < 0.001). Ethanol did not prevent a cold-induced increase in the UCP mRNA levels, although it reduced an increase. The magnitude of the reduction in increase was dependent on the dose, being significant at the dose of 3 g/kg (p < 0.05). The results show that the ethanol-induced drop in body temperature is not necessarily related to IBAT thermogenesis, as indicated by the levels of NE and UCP mRNA.