Opposite effects of gentle handling on body temperature and body weight in rats.

Opposite effects of gentle handling on body temperature and body weight in rats. PHhe aim of this study was to measure the body weight set point when rats are being handled gently and thus experience emotional rise in body temperature. Wistar male rats were used in this experiment, and each rat was its own control. Body weight set point was estimated from the rat's food hoarding behavior. The set point is the intersection of the regression line for hoarding with the X axis. During hoarding sessions the experimenter handled the rat and took its colonic temperature six to eight times, an action sufficient to arouse emotional fever. On alternate days the rats were not handled. Thus, body weight set point was obtained for each rat without handling and with handling. In sessions with handling, rats raised their body temperature, ate less, and defecated more than in control sessions. When handled, the body weight set point declined from 388 +/- 44 g to 366 +/- 47 g (p = 0.048, t = 2,39). The decline in the set point induced by gentle handling is believed to result from an elevation of the hypothalamic CRH.     

Intracerebroventricular taurine in rabbits: effects of normal body temperature, endotoxin fever and hyperthermia produced by PGE1 and amphetamine.

1. Intracerebroventricular (I.C.V.) injections of taurine into rabbits resting at an ambient temperature (Ta) of 10 degrees or 23 degrees C caused hypothermia but at 30 degrees C ambient temperature, rectal temperature was unchanged. 2. An I.C.V. bolus of 0=5 mg taurine immediately followed by a slow infusion of taurine (0-01--0-2 mg/min) into rabbits at 23 degrees C ambient temperature caused sedation and peripheral vasodilation and blocked the febrile response to Salmonella typhosa endotoxin (1 microng/kg i.v.). Sustained fevers, characteristic of fevers caused by central administration of pyrogens, developed after taurine infusions were stopped. Control infusions of taurine at the same rates in the same rabbits when they were afebrile had little effect on rectal temperature. 3. An I.C.V. injection of 0-5 mg taurine reduced the hyperthermia caused by prostaglandin E1 (PGE1; 2 microng) given I.C.V. A dose of 5-0 mg not only blocked PGE1 hyperthermia but also caused marked hypothermia. 4. Bilateral injections of taurine into the preoptic/anterior hypothalamic region, at sites where injections of Salmonella typhosa endotoxin caused long-lasting fevers, had no effect on rectal temperature. Similar injections into the reticular substance of the medulla oblongata, in the region believed to be concerned with a secondary temperature control function, were also without effect on body temperature. 5. Taurine (0-5 and 5-0 mg, I.C.V.) had no consistent effect on hyperthermia induced by amphetamine (2 mg/kg, I.V.) 6. We conclude that the hypothermic effect of taurine is not due to an action on the central neurone pool or pools concerned with the integrative control of thermoregulatory effectors. This amino acid appears to inhibit neuronal activity in efferent pathways which control peripheral vasomotor tone and heat production and to depress the level of arousal. Taurine delays the onset and extends the duration of endotoxin-induced fever, perhaps by two separate action: by inhibiting activity in central thermoregulatory pathways and by promoting accumulation of endogenous pyrogen in the brain.     

Lipectomy, body weight, and body weight set point in rats.

Adult, Wistar male rats were lipectomized or sham lipectomized. The food-hoarding behavior was measured repeatedly and plotted against the animals' body weights. Body weight set point was estimated as the intercept of regression line of hoarding with the X axis. Body fat content was measured with a TOBEC body composition analyzer. Body weight set point, fat content, and girth were obtained initially, after surgery, and after recovery. The hoarding threshold was lowered for 2 weeks after surgery, from 561 +/- 20 to 512 +/- 19 g (lipectomized), and from 582 +/- 15 to 558 +/- 14 g (sham lipectomized). After a 4-week recovery, all rats reached their prelipectomy body weight set point and regained their initial body fat. Five weeks after surgery, no significant difference was found between the body weight set points of lipectomized and sham-lipectomized rats. This indicates that the body weight set point was not mainly modulated by fat depots. The transient lowering of the set point is thought to be due to surgical stress.     

Spontaneous activity, sleep, and body temperature in rats lacking the CCK-A receptor

Because of a genetic mutation, the Otsuka-Long-Evans-Tokushima Fatty (OLETF) rat, a model for human non-insulin-dependent diabetes mellitus (NIDDM), shows no expression of the CCK-A receptor gene. We investigated the spontaneous physical activity, sleep, and body temperature in young OLETF rats that had not yet developed diabetes mellitus, and compared these data with age-matched control LETO (non-diabetic strain, Long-Evans-Tokushima-Otsuka) rats. The amount of large movements during the dark phase for the OLETF rats was significantly less than that of control rats. Thus, the amounts of total daily large movement and the ratio of dark-to-light phase movement in the OLETF rats were less than those of control rats, although the amount of small movement was similar for both groups. The diurnal rhythm of body temperature was similar for both groups. In addition, the amount of and circadian rhythm for each vigilance state and slow-wave activity were similar for the two groups. This study demonstrates that the CCK-A receptor might play a role in affecting the level of motor activity, adding hyperphagia, and the circadian rhythm of large movement in these rats prior to the manifestation of NIDDM. In contrast, a CCK-A receptor deficiency does not appear to affect sleep or body temperature in these rats.     

Estrogenic effects on behavioral thermoregulation and body temperature of rats

Estradiol benzoate increases responding for heat reinforcement of ovariectomized female and intact and castrate male rats placed in the cold. In females, both pre- and postsession rectal temperatures are depressed by the steroid. The maintenance of low temperatures despite increased heat intake suggests that body temperature is regulated at a lower level as a result of estradiol-induced increases in heat loss or decreases in heat production.     

Gonadal hormones and body temperature in rats: effects of estrous cycles, castration and steroid replacement.

The effects of estrous cycles, castration, subcutaneous steroid replacement, and intracranial steroid implants on the colonic temperatures were examined in 3 experiments. In Experiment 1 a rise in colonic temperature was observed at proestrus in intact females, and castration lowered the colonic temperatures of both males and females 1–2 hr before lights out. In Experiment 2 we tested the effects of 3 doses of progesterone and estradiol benzoate on the colonic temperatures of ovariectomized rats. Both hormones raised colonic temperature. The rise in colonic temperature was directly related to the progesterone dose, but it was inversely related to the dose of estradiol benzoate. In Experiment 3, progesterone and estradiol benzoate were implanted in the preoptic area of ovariectomized rats. Although estradiol benzoate in this site had no effect on colonic temperature, there was some suggestion that progesterone may increase colonic temperature when implanted in the preoptic area.     

Short-term effects of streptozotocin-induced diabetes on the electrocardiogram, physical activity and body temperature in rats

A variety of contractility defects have been reported in the streptozotocin (STZ)-induced diabetic rat heart including alterations to the amplitude and time course of cardiac muscle contraction. Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. Electrocardiogram (ECG), physical activity and body temperature data were continuously recorded with a telemetry system before and following the administration of STZ (60 mg kg-1). Heart rate (HR), physical activity and body temperature declined rapidly 3-5 days after administration of STZ. The effects became more conspicuous with time and reached a new steady state approximately 10 days after STZ treatment when HR was 255+/-8 beats min-1 in diabetic rats compared to 348+/-17 beats min-1 in age-matched controls. Heart rate variability (HRV) was also significantly reduced after STZ treatment (18+/-3 beats min-1) compared to controls (36+/-3 beats min-1). Reduced physical activity and/or body temperature may partly underlie the reduction in HR and HRV. Reductions in power spectral density at higher frequencies (2.5-3.5 Hz) suggest that parasympathetic drive to the heart may be altered during the early stages of STZ-induced diabetes. Short-term diabetes-induced changes in vital signs can be effectively tracked by continuous recording using a telemetry system.     

Long-term effects of streptozotocin-induced diabetes on the electrocardiogram, physical activity and body temperature in rats

In vivo biotelemetry studies have demonstrated that short-term streptozotocin (STZ)-induced diabetes is associated with a reduction in heart rate (HR) and heart rate variability (HRV) and prolongation of QT and QRS intervals. This study investigates the long-term effects of STZ-induced diabetes on the electrocardiogram (ECG), physical activity and body temperature. Transmitter devices were surgically implanted in the peritoneal cavity of young adult male Wistar rats. Electrodes from the transmitter were arranged in Einthoven bipolar lead II configuration. ECG, physical activity and body temperature data were continuously recorded with a telemetry system before and following the administration of STZ (60 mg kg⁻¹) for a period of 22 weeks. HR, physical activity and body temperature declined rapidly 3–5 days after the administration of STZ. The effects became conspicuous with time reaching a new steady state approximately 1–2 weeks after STZ treatment. HR at 4 weeks was 268 ± 5 beats min⁻¹ in diabetic rats compared to 347 ± 12 beats min⁻¹ in age-matched controls. HRV at 4 weeks was also significantly reduced after STZ treatment (18 ± 3 beats min⁻¹) compared to controls (33 ± 3 beats min⁻¹). HR and HRV were not additionally altered in either diabetic rats (266 ± 5 and 20 ± 4 beats min⁻¹) or age-matched controls (316 ± 6 and 25 ± 4 beats min⁻¹) at 22 weeks. Reduced physical activity and/or body temperature may partly underlie the reductions in HR and HRV. In addition, the increased power spectral low frequency/high frequency ratio from 4 weeks after STZ treatment may indicate an accompanying disturbance in sympathovagal balance.     

Circadian body temperature rhythm and behavior of rats in thermoclines

When normal adult rats were allowed to choose among different ambient temperatures in a thermocline they selected temperatures about 224 degrees out of phase with their own intracranial temperature circadian oscillations. Without some subsidiary hypotheses, these results are difficult to reconcile with the idea that circadian body temperature rhythm is due to a cyclical shift in the set point temperature.     

Role of lipid peroxidation in enhancement of endotoxin hepatotoxicity.

The present study was undertaken in the rats to examine whether endotoxin hepatotoxicity is enhanced by increased lipid peroxidation. The rats were given 10 ml of water, corn oil or heated and oxygenated corn oil per kg body weight by stomach tube twice a day for 14 days, and then they were injected physiological saline solution or endotoxin (2 or 2.5 mg per kg body weight) into the tail vein. In the rats pretreated with water or corn oil, the activity of serum glutamic pyruvic transaminase was within the normal limit, and there was no conspicuous morphological change in the liver, except for accumulation of fine fat droplets in few liver cells. On the other hand, in the rats pretreated with heated and oxygenated corn oil, containing a large amount of lipid peroxides, accumulation of small fat droplets in the liver cells and a slight elevation of serum transaminase activity were induced. The challenge with endotoxin (2.5 mg per kg body weight) caused focal hepatocellular coagulative necrosis and a marked elevation of serum transaminase activity, irrespective of the sorts of pretreatment, and there was no significant difference in the biochemical change and the histopathological damage between the rats pretreated with water, corn oil and heated and oxygenated corn oil. These results suggest that increased lipid peroxidation does not contribute to the enhancement of endotoxin hepatotoxicity, although it is thought that carbon tetrachloride and ethanol enhance endotoxin hepatotoxicity by synergism between endotoxin and the chemicals through lipid peroxidation.     

Correlations between the circadian patterns of body temperature, metabolism and breathing in rats

It had been demonstrated previously that the circadian patterns of activity and state of arousal are not essential for the manifestation of the daily patterns of pulmonary ventilation (V(E)), tidal volume (V(T)) and breathing frequency (f). In this study we investigated the extent of the linkage between the circadian pattern of breathing and those of body temperature (T(b)) and metabolic rate (oxygen consumption, V(O2), and carbon dioxide production, V(CO2)). Rats were instrumented for measurements of T(b) (by telemetry), and placed in a chamber for continuous 13-day period of measurement of breathing (by a modification of the barometric methodology), and of V(O2) and V(CO2) (by an open flow method). After the first 4 days in control conditions under a 12 h light:12 h dark (L:D) cycle, a perturbation was introduced on day 4, with an L-phase prolongation of 12 h, and on day 9, with an D-phase prolongation of 12 h. During the control days 1-4, all variables had daily oscillations (higher values in D), in phase with each other. During the perturbations (days 4-13), changes in T(b), V(O2) and V(CO2), averaged over the whole period, correlated significantly better with f than with V(T). Day-by-day X-Y loops indicated that V (E), V(T) and f could lead significantly the changes of T(b), V(O2) and V(CO2), and that these relations changed throughout the perturbation period. In addition, f and V(T) did not change necessarily in phase with each other. It is concluded that neither the oscillation in T(b) nor that in metabolism can be considered the direct cause of the daily oscillation of breathing. Presumably, the circadian pattern of breathing reflects the interplay of the daily patterns of many variables, none acting as the primary guide of the breathing daily rhythm.     

Bright light effects on body temperature, alertness, EEG and behavior.

The immediate psychophysiological and behavioral effects of photic stimulation on humans [bright light (BL) of 5K lux or dim light (DL) of 50 lux] were assessed in male subjects (N = 43) under four different conditions. For one condition the same subjects (N = 16) received alternating 90-min blocks of BL and DL during the nighttime h (2300-0800 h) under sustained wakefulness conditions. A second condition was similar to the first except that subjects (N = 8) received photic stimulation during the daytime hours. For the third and fourth conditions different subjects received either continuous BL (N = 10) or continuous DL (N = 9) during the nighttime hours. For the nighttime alternating condition body temperature decreased under DL but either increased or maintained under BL. For the continuous light condition, body temperature dropped sharply across the night under DL but dropped only slightly under BL. Sleepiness was considerably greater under DL than under BL, and the difference became larger as the night progressed. Similarly, alertness, measured by EEG beta activity, was greater under BL, and nighttime performance on behavioral tasks was also generally better. There were no differential effects between BL and DL on any measure during the daytime. These data indicate that light exerts a powerful, immediate effect on physiology and behavior in addition to its powerful influence on circadian organization.     

Enhanced endotoxin effects in plasma fibronectin-deficient rats.

Immunoreactive plasma fibronectin depletion has been associated with the presence of collagen-fibronectin complexes in patients after trauma and in animal models of traumatic and burn injuries. However, the role of plasma fibronectin in the development of sepsis after traumatic and burn injuries in patients is unknown. Treatment of patients and animals with purified human plasma fibronectin ameliorates some of the clinical and metabolic effects of systemic endotoxemia. We report that the induction of immunoreactive plasma fibronectin deficiency by gelatin infusion is associated with enhanced effects of intraperitoneal Escherichia coli endotoxin injection. We have observed a significant increase in the concentrations of ammonia in plasma of treated rats compared with those in control rats administered the same dose of endotoxin.     

Bacterial growth and endotoxin production in lipid emulsion

Klebsiella pneumoniae serotypes 21 and 24 and Enterobacter cloacae were responsible for an outbreak of polymicrobial bacteremia associated with the receipt of lipid emulsion. Since it is recommended that lipid emulsion be kept refrigerated between uses, we undertook a study to determine the growth characteristics of these organisms in lipid emulsion at 5 and 25 degrees C and to examine the use of alternative measurements (pH and endotoxin) to determine contamination by viable and nonviable microorganisms. The bacteria survived but did not proliferate at 5 degrees C; no endotoxin was detected, and the pH remained unchanged. In contrast, after a 2-h lag phase, all three organisms proliferated rapidly when incubated at 25 degrees C and reached concentrations of greater than or equal to 10(7) CFU/ml at 24 h. A decrease in pH was detected after proliferation to 10(7) CFU/ml. Endotoxin was detected after proliferation reached 10(2) CFU/ml. The amount of endotoxin elaborated by the three organisms differed and ranged from 0.013 ng per 8 X 10(2) CFU/ml to 1.3 ng per 2 X 10(3) CFU/ml at 8 h. Our findings show that these microorganisms do not proliferate at refrigerator temperature in lipid emulsion, but can reach significant levels at room temperature. It is, therefore, important to keep lipid emulsion refrigerated between uses. Furthermore, when lipid emulsion contamination is suspected, endotoxin and pH determinations should be considered as possible adjunctive tests while results of bacterial cultures are pending. The results of the present study are applicable to only selected gram-negative bacteria and may not apply to gram-positive bacteria and fungi. However, these data demonstrate that measurement of pH and detection of endotoxin is quite useful when lipid emulsion contamination occurs with selected gram-negative bacteria.     

Action of bacterial endotoxin and lipid A on mitochondrial enzyme activities of cells in culture and subcellular fractions.

Escherichia coli O127:B8 lipopolysaccharide (LPS), prepared by the Westphal procedure, caused a marked decrease in the activities of mitochondrial malate dehydrogenase, succinate dehydrogenase, and adenylate kinase in African green monkey kidney (Vero) cells and primary cultures of mouse liver cells within 2 h after exposure to 10 micrograms of LPS/ml of culture medium. These three enzyme activities leaked into the supernatant fraction, and cytochrome oxidase activity was lost from the mouse liver mitochondrial particulate fraction within 45 min after exposure to 10 micrograms of LPS/mg of protein. Loss malate dehydrogenase activity from isolated mitochondria was also accelerated by LPS from E. coli O26:B6 (Boivin preparation) or Salmonella typhosa O901 (Westphal preparation), and by lipid A from Salmonella minnesota or Shigella sonnei. In addition, LPS and lipid A inhibited state 3 respiration by isolated mitochondria with attendant loss of respiratory control, but adenosine 5'-diphosphate/O ratios were relatively unchanged. Impaired mitochondrial function is an early event after exposure to biologically relevant amounts of LPS or lipid A.     

Rhythms in behaviors, body temperature and plasma corticosterone in SCN lesioned rats given methamphetamine

In aperiodic rats with lesions in the suprachiasmatic nuclei (SCN), rhythms with a circadian period in spontaneous locomotion, wheel-running, feeding, drinking, body temperature and plasma corticosterone were restored by chronic administration of methamphetamine. These rhythms were not entrained by a light-dark cycle. Wheel-running, feeding and drinking rhythms in individual rats were in phase in terms of ultradian bout as well as circadian fluctuation. Rhythms of the intraperitoneal temperature appeared accompanying the spontaneous locomotor rhythm. The phase relation between the two rhythms was similar to that of SCN dependent rhythms. Plasma corticosterone also fluctuated in a circadian fashion. The corticosterone peak preceded the activity onset of locomotor rhythm by a few hours, which was similar to the phase relation observed in the SCN intact animals. It is concluded that the oscillatory mechanism underlying the spontaneous locomotor rhythm in SCN lesioned and methamphetamine treated rats drives also other physiological rhythms. The phase-relations among them were similar to those of rhythms driven by the circadian pacemaker in the SCN.