[Frontiers in Bioscience 15, 564-594, January 1, 2010]
The circadian rhythm of body temperature
Roberto Refinetti1
1
TABLE OF CONTENTS
1. ABSTRACT
This article reviews the literature on the circadian rhythm of body temperature. It starts with a description of the typical pattern of oscillation under standard laboratory conditions, with consideration being given to intra- and interspecies differences. It then addresses the influence of environmental factors (principally ambient temperature and food availability) and biological factors (including locomotor activity, maturation and aging, body size, and reproductive state). A discussion of the interplay of rhythmicity and homeostasis (including both regulatory and heat-exchange processes) is followed by concluding remarks.
2. INTRODUCTION
Repeated measurements of body temperature over time -- allowing the study of 24-hour rhythmicity -- have been conducted in animals and human subjects since at least the mid-1800s (1-6). A few literature reviews, often with limited scopes, have been published occasionally in the last quarter of a century (7-10). The topic is important for at least two reasons: 1) the body temperature rhythm is a convenient marker of the circadian clock for studies on biological rhythms and sleep, and 2) the rhythm reflects a constant conflict between homeostasis and circadian rhythmicity in the control of core temperature in mammals and birds.
This review will start with the description of daily rhythmicity of body temperature in organisms kept under standard laboratory conditions, which usually include: 1) a daily light-dark cycle with 12 hours of light and 12 hours of darkness, 2) constant, neutral ambient temperature, and 3) food and water freely available at all times. Attention will be given to similarities and differences between species and between individuals of the same species.
The influence of non-cyclic environmental factors on the CRT will be discussed next. The discussion will include variations in ambient temperature and in food availability. The influence of cyclic environmental factors, which can synchronize circadian rhythms including the CRT, will not be discussed here because most studies in this area use outputs of the circadian system other than the CRT.
Afterwards, the influence of biological factors will be discussed. Biological factors include variations in the organism's locomotor activity, natural maturation and aging, variations in body size, and changes in reproductive state. These particular biological factors were selected for discussion primarily because much research has been conducted on them, but also because age, body size, and reproductive state are fundamental properties of organisms.
Next, the relationship between the circadian and homeostatic components of body temperature regulation will be discussed with emphasis on both regulatory and heat-exchange processes. The CRT is the result of an interplay of mechanisms of heat production and heat loss controlled by the circadian system.
A final section will summarize the issues previously discussed and will put them all in perspective.
3. RHYTHMICITY UNDER STANDARD CONDITIONS
The expression "circadian rhythm of body temperature" (CRT) will be used throughout this article, but it is important to point out that the expression lacks technical precision. First, the word "circadian" is used in the non-technical sense equivalent to "cycling every 24 hours." In contrast, those who study circadian rhythms reserve the term "circadian" to a rhythm that has been shown to free-run with a period (cycle length) of 18 to 30 hours in the absence of environmental cycles and to be capable of synchronization by environmental cycles with 24-hour periods (11). Of course, once a species has been shown to exhibit a CRT, it is reasonable to assume the existence of a CRT in all members of the species studied thereafter. It is not that clear, however, whether the demonstration of a CRT in one mouse species, for example, justifies the use of the expression in other mouse species. Most researchers would say that this generalization is not justified. What about different breeds, or different age cohorts, of the same species? Such cases remain debatable, and they highlight the problem at hand. Careful researchers will, of course, always avoid unjustified assumptions.
The second imprecision in the expression "circadian rhythm of body temperature" has to do with the phrase "body temperature." It is traditional usage in thermal physiology to reserve the phrase "body temperature" to an abstract temperature computed as the weighed mean of the temperatures of various parts of the body (12). Yet, most studies of the CRT rely on measurements at a single part of the body, usually the intra-abdominal cavity. This measurement of body "core" temperature is most commonly obtained by means of probes inserted into the intestines through the anus or by means of temperature-sensitive radio-transmitters or digital data loggers surgically implanted in the peritoneal space. In small animals, the stress of handling involved in manual measurement of core temperature can significantly affect the animal's temperature, so that the use of radio transmitters or data loggers is a necessity (13-15).
3.1. Pattern of oscillation
Figure 1 shows a typical, averaged body temperature rhythm. The data were obtained with a digital data logger surgically implanted in the intra-abdominal cavity of an Anatolian ground squirrel (Spermophilus xanthoprymnus) prior to the annual hibernation season. In this diurnal animal, temperature is clearly low at night, rises during the day, and falls again at night. The curve is quite smooth because it depicts the average of 10 consecutive days, so that small irregular fluctuations are averaged out.
To the extent that the CRT is a reproducible pattern of oscillation, it can be characterized by parameters that describe "pure" oscillatory phenomena such as sine or cosine functions. As shown in Figure 2, a regular oscillatory process can be characterized by its mesor (mean level), its amplitude (which is approximately half the full range of oscillation), its period (i.e., the duration of the cycle), and its phase (often reported as the position of the peak of the wave, called the acrophase, in relation to an external reference point) (16). Because the CRT is not a pure mathematical function, two other parameters are needed to fully characterize it. One of them is the wave form, which often differs considerably from a sine or cosine wave and sometimes approximates a square wave. Variations in wave form, which are often affected by but are not solely the result of random variability ("biological noise"), invariably affect the strength and reproducibility of the CRT. The magnitude of this reproducibility (or the degree of "stationarity" of the time series) is the sixth parameter of the CRT, often called the robustness of the rhythm (17).
Although a clear oscillatory pattern is often evident by visual inspection of data plots, sometimes computational tools are necessary for the identification of rhythmicity, particularly when the signal-to-noise ratio is low. Numerical analysis is also needed as a means of securing an objective index of rhythmicity and of characterizing the parameters of the oscillation. Various numerical procedures suitable for the analysis of circadian rhythms have been recently reviewed and compared (16). Analysis of the data in Figure 1 reveals that the oscillation has a mean level of 36.8 OC, amplitude of 1.2 OC (range of oscillation of 2.5 OC), acrophase at 13:05 h, a relatively sinusoidal wave form, and robustness of 60% (18).
3.2. Intra- and interspecies differences
Daily rhythmicity of body temperature has been extensively documented in a variety of species. The laboratory rat (Rattus norvegicus) is the species on which the greatest number of studies has been conducted (19-68), but many studies were also conducted on domestic mice (69-86), golden hamsters (87-96), and many other rodent species (97-129). A large number of studies has also been conducted on primates (130-145), including humans (146-184), as well as in dogs (185-188), cats (189-191), goats (192-196), sheep (197-203), horses (203-208), cattle (209-213), other mammals (214-234), and many species of birds (235-252). Although only mammals and birds are true endotherms and have the ability to generate body temperature rhythms in homogeneous thermal environments, other animals are capable of generating body temperature rhythms by selecting different ambient temperatures at different times of the day. Consistent daily variation in the selection of ambient temperature along a temperature gradient has been documented in crustaceans (253-256), fishes (257-261), and reptiles (262-275). At least one reptile -- the green iguana (Iguana iguana) -- is capable of generating a small-amplitude rhythm of body temperature even when housed in a homogeneous thermal environment (276, 277). Honey bee colonies, which function as endothermic pseudo-organisms, also exhibit daily rhythmicity of "body" temperature (278).
Figure 3 facilitates the comparison of the CRTs of three rodent species. This figure shows raw data collected every 6 minutes, so that so-called ultradian oscillations can be seen as high-frequency oscillations superimposed on the 24-hour oscillatory pattern. Inspection of Figure 3 clearly indicates that the rhythms of the nocturnal animals (laboratory rat and fat-tailed gerbil) are characterized by higher temperatures during the night, whereas the rhythm of the diurnal animal (tree shrew) is characterized by higher temperatures during the day. Also evident are differences in wave form: square for the rat, rectangular for the gerbil, and bimodal for the tree shrew. In addition, the amplitudes of the rhythms differ among the species: the daily range of oscillation of the temperature rhythm is less than 2 OC for the rat but more than 4 OC for the tree shrew. Table 1 lists the mean level, range of oscillation, and acrophase (peak time) of the body temperature rhythms of 67 species of mammals and birds. As will be discussed in detail in section 5.3, the mean level of the CRT tends to be higher by more than 1 OC in large-sized species than in small-sized ones, although there is considerable inter-species variability. Also, the body temperature of birds tends to be more than 3 OC higher than that of mammals (on average, 41 OC and 37.5 OC, respectively), and the temperature of marsupial mammals tends to be about 3 OC lower than that of placental mammals. The range of oscillation also varies with body size across species: the range is almost 2 OC narrower in large species than in small ones -- although, again, there is considerable inter-species variability. As for the acrophase, it usually occurs at night in nocturnal animals and during the day in diurnal animals, but it does not seem to be related to body size, except that few large mammals are nocturnal.
Very few studies have addressed directly the question of whether intraindividual differences (i.e., day-to-day differences in the rhythmic pattern exhibited by an individual of a given species) are comparable to interindividual differences (i.e., differences between the average rhythmic patterns of different individuals of the same species). To the best of the author's knowledge, only three studies have addressed the question, one for the rhythm of melatonin secretion (279), one for the rhythm of cortisol secretion (280), and one for the rhythm of body temperature (206). The results of these studies are consistent with the impression that one acquires by reading studies conducted on various individuals of various species, namely, that the variabilities differ in different parameters of the rhythm and in different species but that -- whenever there is a difference between interindividual variability and intraindividual variability -- the latter is always smaller than the former. That is, the day-to-day variability of an individual's rhythm does not exceed the variability between the rhythms of different individuals. Intraindividual variability is consistently smaller than interindividual variability.
Free-running circadian rhythms of body temperature recorded in controlled environments without external temporal cues have been documented in birds (236, 238-242, 244, 246-248, 250, 281, 282), rodents (21, 32, 41, 50-52, 54, 59, 63, 68, 71, 83, 88, 96, 105, 116, 117, 124, 128, 283, 283-291), primates (130, 131, 134, 138, 139, 143-145, 292, 293), including humans (146, 159, 161, 162, 171, 294-300), and other mammals (189-191, 198, 205, 217, 230, 233, 301-303). While these studies provide sufficient evidence of the endogenous nature of the CRT, they do not necessarily demonstrate that the CRT is directly generated by the circadian clock. In principle, the CRT could be generated by another rhythmic process in the body, this other rhythmic process itself being generated by the circadian clock. The influence of biological factors on the CRT is discussed in section 5 below.
4. INFLUENCE OF ENVIRONMENTAL FACTORS
The environment in which an organism lives can affect its circadian rhythms in two major ways: through entrainment and through masking (304, 305). Entrainment is the synchronization of the endogenous clock by an environmental cycle, which is achieved through modulation of the period and phase of the circadian clock. Cyclic and non-cyclic variations in the environment can also mask a circadian rhythm by disturbing its wave form and thus altering the mesor and amplitude and mimicking alterations in period and phase.
Several decades of research on circadian rhythms have generated a large body of knowledge about entrainment mechanisms. The light-dark cycle is a potent entraining agent that has been thoroughly investigated (304, 306). Cycles of ambient temperature (307, 308) and food availability (309, 310) have also been shown to entrain circadian rhythms. Specific masking effects of ambient temperature and food availability on the CRT will be discussed here -- in sections 4.1 and 4.2, respectively.
4.1. Ambient temperature
Most studies of the CRT are conducted under constant temperature conditions in the laboratory or under uncontrolled conditions in the field, but several laboratory studies have used controlled changes in ambient temperature to address the issue of the effects of different ambient temperatures on the CRT.
Ambient temperatures constantly below or above thermoneutrality have not been found to affect the period or phase of the CRT -- and these negative findings are expected, as circadian period is "temperature compensated" even in ectothermic organisms (308, 311). However, exposure to lower temperatures down to 10 or 15 OC has been found to increase the amplitude of the CRT, and this increase in amplitude is often accompanied by a reduction in mesor. Greater CRT amplitude in the cold was observed in studies on squirrel monkeys (140), tree shrews (312), thirteen-lined ground squirrels (128), pigeons (238), mousebirds (313), sunbirds (314), and Australian frogmouth birds (315). On the other hand, no effect of ambient temperature on the amplitude of the CRT was found in rats (39, 66, 312), golden hamsters (312), or mouse lemurs (137). Genuine species differences, rather than differences in experimental methods, may be responsible for the conflicting results.
If the increase in the amplitude of the CRT in a cold environment results mostly from lower nadirs (without higher zeniths), it is often referred to as "torpor," a well-known mechanism of energy conservation analogous to seasonal hibernation (316, 317). Torpor may be induced by cold (or the short photoperiod that naturally accompanies the cold of winter) or simply by restricted food availability, as discussed in section 4.2. Daily torpor is controlled by the circadian system (317) and can, therefore, be thought of as a large-amplitude CRT. However, it is not currently known whether daily torpor involves a distinct physiological process or is simply an extension of the CRT in heterothermic species. A few studies investigating the ambient temperature selected by torpid animals seem to suggest that torpor is a natural extension of the CRT (318, 319).
4.2. Food availability
Because food ingestion is associated with an acute rise in body temperature in various species (197, 245, 320-322), and because animals and humans tend to eat mostly at certain times of the day (323, 324), it is conceivable that the CRT could be a mere side-effect of the circadian rhythm of food consumption. That is, in animals fed ad libitum, the concentration of feeding during the light phase or the dark phase of the light-dark cycle could possibly result in the chronic elevation of body temperature that characterizes the CRT. In reality, however, the CRT persists in the absence of daily oscillation in food consumption. Thus, humans and animals fed small meals at regular intervals throughout the day nonetheless exhibit clear CRTs (172, 180, 205, 325, 326). Furthermore, animals and humans fed no meal at all (that is, subjected to total food deprivation) still show daily rhythmicity in body temperature (24, 156, 188, 202, 219, 230, 237, 327-329). An example is provided in Figure 4. The rectal temperature of a goat was recorded at 3-hour intervals for several days. During the first three days, the animal received a single meal each day (indicated by the arrows). For the next three days, no food was provided. Food deprivation caused a small decline in body temperature, but rhythmicity was clearly preserved.
The fact that the CRT persists in the absence of daily oscillation in food consumption does not imply that disturbance of the usual pattern of feeding cannot affect the CRT. Numerous studies of "food anticipatory activity" in rodents have shown that food restriction can cause both entrainment and masking of the CRT (55, 330-333).
In a number of species, moderate food deprivation induces a reduction in metabolic rate and a fall in body temperature (42, 237, 327, 329, 334-338). What is especially interesting about this phenomenon is its modulation by the circadian system. The hypothermia induced by food deprivation (or chronic food restriction) does not occur indiscriminately. Instead, it is restricted to the inactive phase of the circadian cycle. Although some animals have a natural disposition to exhibit daily torpor even when fed regularly (128, 223, 318, 339-349), various true homeotherms exhibit circadian-modulated starvation-induced hypothermia. This has been documented in doves (282), pigeons (235, 237, 338, 350, 351), quail (328), mousebirds (313, 352), finches (353), pygmy mice (354), deer mice (355), domestic mice (356), rats (42, 43, 329, 357, 358), lemurs (136, 138), sheep (202), and goats (194).
5. INFLUENCE OF BIOLOGICAL FACTORS
Over a century of research on circadian rhythms has produced extensive evidence that circadian rhythms are endogenously generated and that the period of a rhythm is genetically inherited, even if it can be partially and temporarily modulated by environmental factors (359, 360). The fact that the CRT is endogenously generated does not mean, however, that it is generated as an autonomous physiological process. In sections 5.1 through 5.4, I will consider (and reject) the possibility that the CRT is merely a side effect of the circadian rhythm of locomotor activity and will discuss how the CRT is affected by the developmental state of an organism, by its body size, and by its reproductive state.
5.1. Locomotor activity
The daily/circadian rhythms of locomotor activity and body temperature have been simultaneously monitored in many studies on various species (30, 31, 51, 74, 88, 95, 110, 130, 135, 159, 248, 285, 286, 361, 362). Generally, the temporal courses of the two rhythms are very similar. In diurnal animals, the activity and body temperature rhythms exhibit high values during the day and low values during the night. Conversely, the activity and body temperature rhythms of nocturnal animals exhibit high values during the night and low values during the day. In both humans and rodents, body temperature starts to ascend slowly several hours before awakening and then rises abruptly (more so in rodents than in humans) at wake time (363).
Because the rhythms of body temperature and activity proceed closely together -- both under a light-dark cycle and in constant conditions -- it is natural to wonder whether the temperature rhythm is not simply a consequence of the activity rhythm. Indeed, it is well known that acute episodes of physical activity and exercise can elevate body temperature in humans (2, 176, 364-367) and other vertebrates (91, 134, 204, 220, 368-370), so that the daily elevation in body temperature associated with circadian rhythmicity might be a direct result of increased activity.
In order to investigate the potential causal link between the activity rhythm and the temperature rhythm, several researchers recorded the body temperature rhythm of human subjects maintained in continuous bed rest (156, 158, 371), or undergoing a "constant routine" protocol, which involves bed rest as well as sleep deprivation and the ingestion of frequent, equal-size meals (172, 180, 325, 326). Although the amplitude of the rhythm is reduced under this condition, robust rhythmicity persists. Thus, while the activity rhythm may alter the amplitude and shape of the body temperature rhythm, it does not cause it. Bed rest cannot be used with animals, but the autonomy of the CRT has been demonstrated by analysis of the day-night difference in the correlation between the rhythms of activity and temperature. Although nocturnal animals are generally more active at night than during the day, their body temperature is higher at night regardless of the actual activity level (51, 92, 95, 130, 372, 373). Conversely, the body temperature of diurnal animals is higher during the day regardless of the actual activity level (363). Thus, we may confidently say that the body temperature rhythm in animals, as in humans, is not caused by the activity rhythm.
The fact that the CRT is not caused by the activity rhythm does not imply that the CRT cannot be enhanced or disrupted (masked) by changes in activity. As a matter of fact, some researchers argue that the CRT is so strongly masked by changes in activity in free-living subjects that it should not be relied upon as a marker of the state of the circadian clock. Some argue that masking can be mathematically filtered out (374), whereas others recommend that the CRT be replaced by the rhythm of melatonin secretion as a reliable marker of the state of the clock (375). The advantages of the CRT include tradition, ease of measurement, and demonstrated autonomy from the activity rhythm, whereas the susceptibility to masking is a major disadvantage. The melatonin rhythm has the advantage of being resistant to masking caused by activity but has several disadvantages, including the need for frequent collection of blood (or saliva) samples and a high susceptibility to masking caused by environmental light during the night.
5.2. Maturation and aging
In rats, a rhythm of body temperature with a range of oscillation of 2-4 OC is observed on the day after birth, but it seems to vanish by 15-20 days of age (376-381). Weak rhythmicity appears again at 25 days of age and attains the adult range (1.6 OC) at 45 days of age (382). Because the early temperature rhythm vanishes in a few days and is observed only when the pups are kept at an ambient temperature below thermoneutrality, this rhythm is thought not to be a true precursor of the adult rhythm of body temperature but a form of cold-induced torpor (378, 383). In rabbits, temperature rhythmicity can be observed as early as 4 or 5 days after birth in pups allowed to remain with the doe (303, 384), but not in pups kept in isolation with continuous intra-esophageal feeding (379).
Newborn calves lack daily rhythmicity of body temperature. Daily rhythms comparable to those of adults are not observed until two months after birth (209). One research group reported the presence of rhythmicity two weeks after birth (385), but their calves were exposed to large daily fluctuations in ambient temperature (about 20 OC), which probably caused the fluctuation in body temperature. In calves maintained under constant ambient temperature, no difference between measurements taken at dawn and measurements taken at dusk was found for the first 10 days of life. Later on, measurements taken at dawn decreased gradually until a stable dusk-dawn difference of about 1 OC was achieved between 50 and 60 days after birth (209).
Lambs (young sheep) and foals (young horses) also develop daily rhythms of body temperature during early life, although adult rhythms seem to be attained earlier than in calves, as a stable dusk-dawn difference is achieved about one month after birth (386). Evidently, different species develop the body temperature rhythm at different rates. In dogs, puppies of three different breeds failed to exhibit statistically significant daily rhythmicity for several days after birth. Regardless of breed or sex, rhythmicity matured over several weeks and attained a stable level by 6 weeks after birth (387). The reasons for the differences in timing among calves, dogs, lambs, and foals are not evident. Different species of domestic animals exhibit different parameters of body temperature rhythmicity in adulthood (388), and it is to be expected that differences will also exist in the ontogenetic development of rhythmicity.
Newborn human babies do not have a rhythm of body temperature. The body temperature of a newborn oscillates randomly; a daily pattern is noticeable at 3 months of age; and a mature daily rhythm is not reached until a year or more after birth (389, 390).
Despite interspecies differences in the rate of maturation, the fact that the CRT is not present at birth seems to be a common finding. The absence of the CRT in early life may be due to immaturity of the circadian system, to immaturity of mechanisms of heat gain and heat loss, or to both. Immaturity of the circadian system is suggested by the fact that other bodily rhythms also undergo maturation. For instance, the rhythm of melatonin secretion is present immediately after birth in seals (391), but only two weeks after birth in hamsters and rats (392), and only three months after birth in humans (393, 394). However, the delay in the expression of rhythms is most likely due to the development of mechanisms downstream from the circadian pacemaker, because, at least in rats and sheep, the pacemaker itself is already oscillating before birth (395-399). Furthermore, the thermoregulatory system is known to undergo maturation in young mammals and birds, principally through the development of heat conservation mechanisms (400).
At the other end of the age spectrum, the CRT is affected by aging. By far the best characterized alteration in the circadian system related to aging is a reduction in the amplitude of circadian rhythms (401-403). Reduction in the amplitude of the body temperature rhythm in old age has been documented in humans (162, 163, 404, 405) as well as in various rodent species (53, 60, 61, 77, 119, 406-410).
Aging seems to also be associated with a change in the phase and period of circadian rhythms. A small advance in the phase angle of entrainment in old age has been documented in humans (163, 411-414) and rodents (61, 78, 407), although few of these studies monitored the CRT. Studies on golden hamsters have generally found that circadian period is shortened in old age (415-421), and shortening of circadian period was also observed in deer mice (415), and laboratory rats (422). However, lengthening of circadian period was observed in aging domestic mice (423, 424) and canaries (425). In humans, one study found no difference between the free-running periods of young and old subjects (426), whereas another found shorter periods in older subjects (162). Clearly, more studies are needed to clarify these apparently conflicting results.
5.3. Body size
Many years ago, Aschoff pointed out that the amplitude of the CRT is 3 to 6 times smaller in large animals than in small animals in the body weight range from 10 g to 1 kg (427). The data from 135 independent studies shown in Figure 5 (panel A) confirm that the amplitude is about 3 times smaller in large mammals than in small animals in the body mass range from 10 g to 1,000 kg. Presumably, large bodies buffer the effects of the oscillations in heat production and heat loss responsible for the CRT, although the effect is modest (as indicated by the relatively small correlation coefficient of -0.26). Curiously, body size has the opposite effect on the mean level of the CRT (Figure 5, panel B). Animals in the 1,000-kg range have, on average, body temperatures 0.6 OC higher than the body temperatures of animals in the 10-g range. Again, this is presumably due to the greater thermal inertia of large animals, and again caution should be exercised in the interpretation of this weak albeit statistically significant relationship. A recent literature survey based on 125 independent studies in mammals has also confirmed Aschoff's prediction (428). The amplitude of the body temperature rhythm was found to be smaller, and the mean level to be higher, in large animals than in small animals.
Interspecies studies of the relationship between body temperature and body size based on literature surveys have either failed to identify a significant correlation (429, 430) or identified a weak positive correlation (427, 428, 431). Curiously, intraspecies studies in dogs (387) and humans (432) identified a significant inverse correlation between body temperature and body mass. The data for dogs are shown in Figure 6. The negative correlation between body temperature and body size has a coefficient of -0.57. Why interspecies coefficients should be positive and intraspecies coefficients be negative is not evident, but there must clearly be differences between species. As a matter of fact, a recent literature review identified no significant relationship between temperature and body mass in mammals overall but uncovered significant relationships for particular subgroups (433). For instance, a positive scaling relationship was found in bats, whereas a negative scaling relationship was found in artiodactyls. The finding that the scaling of body temperature is positive in some phylogenetic groups but negative in others implies that the causes of the scaling must be found in ecological factors that affected the evolution of different phylogenetic groups differently.
5.4. Reproductive state
Most female animals do not ovulate on demand, so that reproduction is possible only during the appropriate phase of an ovulatory cycle (434). The reproductive cycle involves not only timed ovulation but also estrous rhythmicity in hormonal secretions (250, 435-451), vaginal discharges (234, 444, 448, 449, 452-454), behavioral sexual receptivity (445, 446, 451, 453, 455-458), and locomotor activity (66, 114, 234, 435, 437, 452, 459-463). In addition, many species of mammals and birds exhibit estrous rhythmicity in body temperature (66, 114, 209, 234, 240, 242, 243, 250, 438, 442, 452, 461-470). All of these processes can mask the CRT in multiple ways. For this reason, most studies of daily and circadian rhythms of body temperature (or of locomotor activity, for that matter) are conducted on males.
6. RHYTHMICITY AND HOMEOSTASIS
The homeostatic control of body temperature has the goal of ensuring stability -- that is, of preventing deviations from an ideal set point. On the other hand, the circadian control of body temperature imposes a persistent oscillation in body temperature. Somehow, these two antithetic processes must be integrated. How this is accomplished in terms of physiological control will be discussed in section 6.1. How it is accomplished in terms of effector mechanisms will be discussed in section 6.2.
6.1. Regulatory process
Thermal physiologists have generally assumed that the CRT is primarily under homeostatic control and is secondarily modulated by the circadian system through an oscillation in the thermoregulatory set point (293, 471-473). According to this view, the circadian pacemaker acts on the thermoregulatory thermostat so that the set point is elevated during subjective day and lowered during subjective night in diurnal animals (or vice versa in nocturnal animals). An alternate arrangement, more logical from the viewpoint of circadian biologists, would be to have the circadian oscillation in body temperature primarily under circadian control, bypassing the thermoregulatory set point, and being secondarily modulated by the thermoregulatory system. Research conducted in the past 10 years or so strongly supports the alternate explanation.
The idea that the CRT might result from a daily oscillation of the thermoregulatory set point seemed to be supported by laboratory evidence that autonomic heat loss responses are activated during the circadian phase of low body temperature, and heat conservation responses are activated during the phase of high body temperature, in rats (474), pigeons (475, 476), and humans (148, 477-479). The reasoning was that, for instance, enhanced thermogenesis during the circadian phase when body temperature is high implies an elevation of the set point (because, presumably, the elevation in the set point was responsible for the enhanced heat production). The finding that injection of antipyretics could reduce the amplitude of the CRT of otherwise undisturbed rats (58) provided further support for the notion of circadian modulation of the set point.
What was wrong with the preceding reasoning was that the measurement of autonomic thermoregulatory responses at different times of the day does not really tell us anything about the state of the set point. It tells us only that heat production and heat loss mechanisms are being activated -- and it is a thermodynamic necessity that mechanisms of heat production or heat loss must be activated in order for body temperature to change (if ambient temperature is kept constant). In other words, the studies that allegedly supported the set-point explanation of the CRT failed to evaluate set point changes. In order to judge whether there is circadian modulation of the thermoregulatory set point, one must be able to monitor the set point. In order to measure the state of the set point, one needs a variable that is not normally required for the production of the body temperature rhythm but that, at the same time, does reflect the operation of the set point. It is known that autonomic and behavioral thermoregulatory responses can complement each other in the homeostatic control of body temperature (480-486), and it was pointed out above that the body temperature rhythm of endotherms does not require behavioral responses. Therefore, the use of behavioral responses can provide a reliable measure of the state of the set point.
The first investigator to directly address the issue was probably Hensel, in 1978, who studied the thermal sensation evoked by warming of the hand of human subjects at different times of the day and noticed that warm stimuli were perceived as more pleasant during the circadian phase of low body temperature than during the phase of high temperature (487). The following year, Carlisle noticed that rats exposed to the cold would press a lever for heat more vigorously during the phase of low body temperature than during the phase of high temperature (488). Research in many other laboratories over the years, using a variety of behavioral research techniques, has documented that higher ambient temperatures are preferred during the phase of low body temperature, and lower ambient temperatures are preferred during the phase of high body temperature, in rats (22, 45, 48, 329, 489-491), mice (492), golden hamsters (93, 490, 493), Siberian hamsters (319), fat-tailed gerbils (118), degus (115), stripe-faced dunnarts (318), tree shrews (108), flying squirrels (108), lemurs (494), and humans (495-498).
Figure 7 illustrates the phase opposition between the rhythms of body temperature and of preferred ambient temperature in fat-tailed gerbils (Pachyuromys duprasi) tested in a temperature gradient. As expected for a nocturnal animal, body temperature was high during the night and low during the day. The rhythm of behavioral temperature selection was, however, 180O out of phase with the rhythm of body temperature. Clearly, higher environmental temperatures are selected when body temperature is low, and vice versa. Thus, the oscillation of the set point cannot possibly be responsible for the temperature rhythm. As a matter of fact, there is no reason to assume that the set point oscillates at all (499, 500). As body temperature oscillates, the animals behaviorally counteract the oscillation to defend the unaltered set point. The thermoregulatory system actually opposes the oscillation of body temperature imposed by the circadian system.
The thermoregulatory system's opposition to the circadian oscillation of body temperature is evidently not fully successful, as witnessed by the very existence of the rhythm. However, the amplitude of the temperature rhythm is effectively reduced by the action of the thermoregulatory system. This has been shown in two ways. One way was by comparing the amplitude of the rhythm in animals maintained in a constant-temperature environment with the amplitude in animals allowed to continually select their environmental temperature in a gradient. The amplitude of the body temperature rhythm was reduced in tree shrews and flying squirrels allowed to select their environmental temperature (108). The other way was by impairing the thermoregulatory system through surgical ablation of the main thermoregulatory center in the preoptic area of the brain. The amplitude of the body temperature rhythm was greatly enhanced in rats and golden hamsters with preoptic lesions (501-503), implying that ablation of the preoptic area releases the circadian oscillation of body temperature from inhibitory control. Thus, it can be inferred that the thermoregulatory center in the preoptic area of unlesioned animals restricts the oscillation of body temperature to an acceptable range. In other words, the circadian system generates an oscillatory signal that is communicated to the organs responsible for heat production and heat loss. At the same time, the thermoregulatory system generates a set point that, like most control systems, has a margin of hysteresis error. The integrated output of the two systems is an oscillation whose amplitude is restricted to the boundaries of hysteresis error.
6.2. Heat-exchange process
In order to produce a CRT, the body must produce an oscillation in the amount of metabolic heat produced and/or in the amount of heat lost to the environment. Aschoff reasoned early on that both heat production and heat loss needed to oscillate, and that the oscillation of heat loss needed to lag behind the oscillation of heat production (7). This has indeed been observed in rats (64, 287), squirrel monkeys (141, 293), and humans (172, 504). An example is shown in Figure 8. Cosine waves were fitted to the raw data of body temperature, heat production, and heat loss of a rat (top three graphs). The vertical dashed lines indicate the acrophases of the rhythms. Notice that heat production leads body temperature by 1.3 hours, whereas heat loss trails body temperature by 0.9 hour. If heat balance is calculated (bottom panel), a phase difference of 6 hours is found. That is, the heat-balance rhythm leads the temperature rhythm by 6 hours. This phase difference is presumably due to thermal inertia of the body and should be different in animals of different body sizes (427).
7. PERSPECTIVE
Daily oscillation in the body core temperature of mammals and birds has been documented in numerous studies on a large number of species. Body temperature is generally higher during the day in diurnal species and higher during the night in nocturnal species. The mean level of the oscillation is between 36 and 41 OC in most species, and the daily range of oscillation is between 1 and 5 OC. Under constant environmental conditions, the rhythm free-runs with a period shorter or longer than 24 hours, depending on the species.
The CRT is robust under constant, neutral environmental conditions, but its amplitude is enhanced in cold environments in some species. Enhanced amplitude can also be observed in animals with restricted access to food. Although the CRT persists in the absence of daily rhythmicity in activity, activity can greatly affect the CRT. Maturational stage, body size, and reproductive state can also affect the CRT.
The circadian oscillation in body temperature is primarily under circadian control, bypassing the thermoregulatory set point, and is secondarily modulated by the thermoregulatory system. The actual change in temperature is achieved by modulation of heat balance, with the oscillation of heat loss lagging behind the oscillation of heat production by a few hours.
Understanding the causes and properties of the CRT is important because homeothermic endothermy provides physiological and ecological benefits believed to be responsible for the adaptive success of birds and mammals in a wide range of aerial, aquatic, and terrestrial environments (505). Thus, the violation of homeothermy represented by the CRT must be seen as much more than just a curious deviation from an ideal pattern. Although it is generally assumed that hibernation and torpor are relatively recent specializations arising from homeothermic ancestors, it has been proposed that heterothermy may have actually preceded homeothermy in vertebrates (506). Thus, the CRT may very well be a mild recent form of an ancient process of daily torpidity. Interestingly, it has been extensively documented that extant ectothermic species, particularly reptiles (262-275), can generate CRTs if provided with the opportunity to select the temperature of their environment, which further supports the notion of an ancestral origin of daily/circadian rhythmicity. It is possible, therefore, that the evolutionarily "new" drive to maintain homeostasis in homeotherms conflicts with the "old" universal drive to oscillate body temperature -- and this may explain the opposition between the thermoregulatory system and the circadian system in the control of body temperature in contemporary homeotherms.
8. REFERENCES
1. C. Chossat: Recherches expérimentales sur l'inanition. Ann Sci Nat Série 2 20, 293-326 (1843)
2. J. Davy: On the temperature of man. Philos Trans R Soc Lond 135, 319-333 (1845)
doi:10.1098/rstl.1845.0014
3. W. Ogle: On the diurnal variations in the temperature of the human body in health. St. George's Hosp Rep 1, 221-245 (1866)
4. A. Rattray: On some of the more important physiological changes induced in the human economy by change of climate, as from temperate to tropical, and the reverse. Proc R Soc Lond 18, 513-528 (1870)
doi:10.1098/rspl.1869.0088
5. E. Maurel: Expériences sur les variations nycthémérales de la température normale. C R Séances Soc Biol Paris 37, 588 (1884)
6. F. Hobday: Notes on physiological temperatures. J Comp Pathol Ther 9, 286-314 (1896)
7. J. Aschoff: Circadian control of body temperature. J Therm Biol 8, 143-147 (1983)
doi:10.1016/0306-4565(83)90094-3
8. G. L. Hahn: Body temperature rhythms in farm animals: a review and reassessment relative to environmental influences. In: Driscoll, D. & Box, E. O. (Eds.). Proceedings of the 11th ISB Congress. The Hague: SPB Academic Publishing, pp. 325-337
9. R. Refinetti and M. Menaker: The circadian rhythm of body temperature. Physiol Behav 51, 613-637 (1992)
doi:10.1016/0031-9384(92)90188-8
10. J. Waterhouse, B. Drust, D. Weinert, B. Edwards, W. Gregson, G. Atkinson, S. Kao, S. Aizawa and T. Reilly: The circadian rhythm of core temperature: origin and some implications for exercise performance. Chrobiol Int 22, 207-225 (2005)
doi:10.1081/CBI-200053477
PMid:16021839
11. J. Aschoff: A survey on biological rhythms. In: Aschoff, J. (Ed.). Biological Rhythms (Handbook of Behavioral Neurobiology Volume 4). New York: Plenum, pp. 3-10
12. D. Minard: Body heat content. In: Hardy, J. D., Gagge, A. P. & Stolwijk, J. A. J. (Eds.). Physiological and Behavioral Temperature Regulation. Springfield, Ill.: Charles C. Thomas, pp. 345-357
13. S. Poole and J. D. Stephenson: Core temperature: some shortcomings of rectal temperature measurements. Physiol Behav 18, 203-205 (1977)
doi:10.1016/0031-9384(77)90122-6
14. J. Georgiev: Influence of environmental conditions and handling on the temperature rhythm of the rat. Biotelem Patient Monit 5, 229-234 (1978)
15. K. Kramer, H. P. Voss, J. Grimbergen and A. Bast: Circadian rhythms of heart rate, body temperature, and locomotor activity in freely moving mice measured with radio telemetry. Lab Anim 27(8), 23-26 (1998)
16. R. Refinetti, G. Cornélissen and F. Halberg: Procedures for numerical analysis of circadian rhythms. Biol Rhythm Res 38, 275-325 (2007)
doi:10.1080/09291010600903692
17. R. Refinetti: Non-stationary time series and the robustness of circadian rhythms. J Theor Biol 227, 571-581 (2004)
doi:10.1016/j.jtbi.2003.11.032
PMid:15038991
18. M. K. Gür, R. Refinetti and H. Gür: Daily rhythmicity and hibernation in the Anatolian ground squirrel under natural and laboratory conditions. J Comp Physiol B 179, 155-164 (2009)
doi:10.1007/s00360-008-0298-0
19. R. Refinetti: Comparison of the body temperature rhythms of diurnal and nocturnal rodents. J Exp Zool 275, 67-70 (1996)
doi:10.1002/(SICI)1097-010X(19960501)275:1<67::AID-JEZ10>3.0.CO;2-U
PMid:8708632
20. M. J. Kluger, C. A. Conn, B. Franklin, R. Freter and G. D. Abrams: Effect of gastrointestinal flora on body temperature of rats and mice. Am J Physiol 258, R552-R557 (1990)
21. R. E. Mistlberger, H. Lukman and B. G. Nadeau: Circadian rhythms in the Zucker obese rat: assessment and intervention. Appetite 30, 255-267 (1998)
doi:10.1006/appe.1997.0134
PMid:9632457
22. E. Briese: Rats prefer ambient temperatures out of phase with their body temperature circadian rhythm. Brain Res 345, 389-393 (1985)
doi:10.1016/0006-8993(85)91023-6
PMid:4041898
23. O. Shido, S. Sakurada and T. Nagasaka: Effect of heat acclimation on diurnal changes in body temperature and locomotor activity in rats. J Physiol Lond 433, 59-71 (1991)
24. O. Shido, S. Sakurada, W. Kohda and T. Nagasaka: Day-night changes of body temperature and feeding in heat-acclimated rats. Physiol Behav 55, 935-939 (1994)
doi:10.1016/0031-9384(94)90082-5
25. D. L. Berkey, K. W. Meeuwsen and C. C. Barney: Measurements of core temperature in spontaneously hypertensive rats by radiotelemetry. Am J Physiol 258, R743-R749 (1990)
26. R. M. Morley, C. A. Conn, M. J. Kluger and A. J. Vander: Temperature regulation in biotelemetered spontaneously hypertensive rats. Am J Physiol 258, R1064-R1069 (1990)
27. E. Peloso, M. Wachulec and E. Satinoff: Stress-induced hyperthermia depends on both time of day and light condition. J Biol Rhythms 17, 164-170 (2002)
doi:10.1177/074873002129002456
PMid:12002163
28. B. Bruguerolle and X. Roucoules: Time-dependent changes in body temperature rhythm induced in rats by brewer's yeast injection. Chrobiol Int 11, 180-186 (1994)
doi:10.3109/07420529409057238
PMid:8082227
29. Y. Yoshida, N. Fujiki, T. Nakajima, B. Ripley, H. Matsumura, H. Yoneda, E. Mignot and S. Nishino: Fluctuation of extracellular hypocretin-1 (orexin A) levels in the rat in relation to the light-dark cycle and sleep-wake activitties. Eur J Neurosci 14, 1075-1081 (2001)
doi:10.1046/j.0953-816x.2001.01725.x
PMid:11683899
30. M. Meinrath and M. R. D'Amato: Interrelationships among heart rate, activity, and body temperature in the rat. Physiol Behav 22, 491-498 (1979)
doi:10.1016/0031-9384(79)90015-5
31. E. M. W. Kittrell and E. Satinoff: Diurnal rhythms of body temperature, drinking and activity over reproductive cycles. Physiol Behav 42, 477-484 (1988)
doi:10.1016/0031-9384(88)90180-1
32. R. Refinetti: Experimentally induced disruption of the diurnal rhythm of body temperature of the rat. Biotemas 3(2), 47-58 (1990)
33. M. C. Fioretti, C. Riccardi, E. Menconi and L. Martini: Control of the circadian rhythm of body temperature in the rat. Life Sci 14, 2111-2119 (1974)
doi:10.1016/0024-3205(74)90093-9
PMid:4847803
34. F. Halberg, H. A. Zander, M. W. Houglum and H. R. Mühlemann: Daily variations in tissue mitoses, blood eosinophils and rectal temperatures of rats. Am J Physiol 177, 361-366 (1954)
35. J. A. Thornhill, M. Hirst and C. W. Gowdey: Measurement of diurnal core temperatures of rats in operant cages by AM telemetry. Can J Physiol Pharmacol 56, 1047-1050 (1978)
36. R. Abrams and H. T. Hammel: Cyclic variations in hypothalamic temperature in unanesthetized rats. Am J Physiol 208, 698-702 (1965)
37. G. H. Miles: Telemetering techniques for periodicity studies. Ann N Y Acad Sci 98, 858-865 (1962)
38. H. Tanaka, M. Yanase, K. Kanosue and T. Nakayama: Circadian variation of thermoregulatory responses during exercise in rats. Am J Physiol 258, R836-R841 (1990)
39. B. Roussel, G. Chouvet and G. Debilly: Rythmes circadiens des températures internes et ambiance thermique chez le rat. Pflügers Arch 365, 183-189 (1976)
doi:10.1007/BF01067017
PMid:988557
40. W. Tornatzky and K. A. Miczek: Long-term impairment of autonomic circadian rhythms after brief intermittent social stress. Physiol Behav 53, 983-993 (1993)
doi:10.1016/0031-9384(93)90278-N
41. M. Ikeda and S. Inoué: Simultaneous recording of circadian rhythms of brain and intraperitoneal temperatures and locomotor and drinking activities in the rat. Biol Rhythm Res 29, 142-150 (1998)
doi:10.1076/brhm.29.2.142.1451
42. T. Yoda, L. I. Crawshaw, K. Yoshida, L. Su, T. Hosono, O. Shido, S. Sakurada, Y. Fukuda and K. Kanosue: Effects of food deprivation on daily changes in body temperature and behavioral thermoregulation in rats. Am J Physiol 278, R133-R139 (2000)
43. K. Nagashima, S. Nakai, K. Matsue, M. Konishi, M. Tanaka and K. Kanosue: Effects of fasting on thermoregulatory processes and the daily oscillations in rats. Am J Physiol 284, R1486-R1493 (2003)
44. Y. Isobe, S. Takaba and K. Ohara: Diurnal variation of thermal resistance in rats. Can J Physiol Pharmacol 58, 1174-1179 (1980)
45. C. J. Gordon: 24-Hour control of body temperature in rats. I. Integration of behavioral and autonomic effectors. Am J Physiol 267, R71-R77 (1994)
46. R. Stephenson, K. S. Liao, H. Hamrahi and R. L. Horner: Circadian rhythms and sleep have additive effects on respiration in the rat. J Physiol Lond 536, 225-235 (2001)
doi:10.1111/j.1469-7793.2001.00225.x
PMid:11579171 PMCid:2278848
47. E. L. Seifert and J. P. Mortola: The circadian pattern of breathing in conscious adult rats. Resp Physiol 129, 297-305 (2002)
doi:10.1016/S0034-5687(01)00316-4
PMid:11788133
48. B. Ray, H. N. Mallick and V. M. Kumar: Changes in thermal preference, sleep-wakefulness, body temperature and locomotor activity of rats during continuous recording for 24 hours. Behav Brain Res 154, 519-526 (2004)
doi:10.1016/j.bbr.2004.03.021
PMid:15313041
49. J. M. De Castro: Diurnal rhythms of behavioral effects on core temperature. Physiol Behav 21, 883-886 (1978)
doi:10.1016/0031-9384(78)90160-9
50. K. Honma and T. Hiroshige: Internal synchronization among several circadian rhythms in rats under constant light. Am J Physiol 235, R243-R249 (1978)
51. K. Honma and T. Hiroshige: Simultaneous determination of circadian rhythms of locomotor activity and body temperature in the rat. Jap J Physiol 28, 159-169 (1978)
52. M. Ikeda, M. Sagara and S. Inoué: Continuous exposure to dim illumination uncouples temporal patterns of sleep, body temperature, locomotion and drinking behavior in the rat. Neurosci Lett 279, 185-189 (2000)
doi:10.1016/S0304-3940(99)00943-X
PMid:10688060
53. C. Benstaali, A. Bogdan and Y. Touitou: Effect of a short photoperiod on circadian rhythms of body temperature and motor activity in old rats. Pflügers Arch 444, 73-79 (2002)
doi:10.1007/s00424-002-0795-z
PMid:11976918
54. P. Deprés-Brummer, F. Lévi, G. Metzger and Y. Touitou: Light-induced suppression of the rat circadian system. Am J Physiol 268, R1111-R1116 (1995)
55. D. T. Krieger: Food and water restriction shifts corticosterone, temperature, activity and brain amine periodicity. Endocrinology 95, 1195-1201 (1974)
doi:10.1210/endo-95-5-1195
PMid:4426285
56. H. M. Murphy, C. H. Wideman and G. R. Nadzam: A laboratory animal model of human shift work. Integr Physiol Behav Sci 38, 316-328 (2003)
doi:10.1007/BF02688860
57. C. T. Fischette, H. M. Edinger and A. Siegel: Temporary desynchronization among circadian rhythms with lateral fornix ablation. Brain Res 229, 85-101 (1981)
doi:10.1016/0006-8993(81)90748-4
PMid:7306813
58. W. E. Scales and M. J. Kluger: Effect of antipyretic drugs on circadian rhythm in body temperature of rats. Am J Physiol 253, R306-R313 (1987)
59. W. S. Warren and V. M. Cassone: The pineal gland: photoreception and coupling of behavioral, metabolic, and cardiovascular circadian outputs. J Biol Rhythms 10, 64-79 (1995)
doi:10.1177/074873049501000106
PMid:7632982
60. R. Refinetti, H. Ma and E. Satinoff: Body temperature rhythms, cold tolerance, and fever in young and old rats of both genders. Exp Gerontol 25, 533-543 (1990)
doi:10.1016/0531-5565(90)90019-X
PMid:2097169
61. H. Li and E. Satinoff: Changes in circadian rhythms of body temperature and sleep in old rats. Am J Physiol 269, R208-R214 (1995)
62. C. J. Gordon and A. H. Rezvani: Genetic selection of rats with high and low body temperatures. J Therm Biol 26, 223-229 (2001)
doi:10.1016/S0306-4565(00)00046-2
PMid:11240229
63. F. Spencer, H. W. Shirer and J. M. Yochim: Core temperature in the female rat: effect of pinealectomy or altered lighting. Am J Physiol 231, 355-360 (1976)
64. O. Shido, Y. Sugano, and T. Nagasaka: Circadian change of heat loss in response to change in core temperature in rats. J Therm Biol 11, 199-202 (1986)
doi:10.1016/0306-4565(86)90002-1
65. T. Severinsen and N. A. Øritsland: Endotoxin induced prolonged fever in rats. J Therm Biol 16, 167-171 (1991)
doi:10.1016/0306-4565(91)90039-5
66. Y. Yang and C. J. Gordon: Ambient temperature limits and stability of temperature regulation in telemetered male and female rats. J Therm Biol 21, 353-363 (1996)
doi:10.1016/S0306-4565(96)00021-6
67. L. Tsai, Y. Tsai, K. Huang, Y. Huang and J. Tzeng: Repeated light-dark shifts speed up body weight gain in male F344 rats. Am J Physiol 289, E212-E217 (2005)
68. M. Cuesta, D. Clesse, P. Pévet and E. Challet: From daily behavior to hormonal and neurotransmitter rhythms: comparison between diurnal and nocturnal rat species. Horm Behav 55, 338-347 (2009)
doi:10.1016/j.yhbeh.2008.10.015
PMid:19027018
69. L. R. Leon, L. D. Walker, D. A. DuBose and L. A. Stephenson: Biotelemetry transmitter implantation in rodents: impact on growth and circadian rhythms. Am J Physiol 286, R967-R974 (2004)
70. A. J. Keeney, S. Hogg and C. A. Marsden: Alterations in core body temperature, locomotor activity, and corticosterone following acute and repeated social defeat of male NMRI mice. Physiol Behav 74, 177-184 (2001)
doi:10.1016/S0031-9384(01)00541-8
71. P. J. Shiromani, M. Xu, E. M. Winston, S. N. Shiromani, D. Gerashchenko and D. R. Weaver: Sleep rhythmicity and homeostasis in mice with targeted disruption of mPeriod genes. Am J Physiol 287, R47-R57 (2004)
72. M. V. Berezkin, V. F. Kudinova, A. N. Batygov, L. E. Ponomareva and G. N. Zhukova: Effect of lighting conditions on circadian rhythm of rectal temperature in mice. Bull Exp Biol Med 106, 1337-1340 (1989)
doi:10.1007/BF00834513
73. C. A. Conn, B. Franklin, R. Freter and M. J. Kluger: Role of gram-negative and gram-positive gastrointestinal flora in temperature regulation of mice. Am J Physiol 261, R1358-R1363 (1991)
74. D. Weinert and J. Waterhouse: Diurnally changing effects of locomotor activity on body temperature in laboratory mice. Physiol Behav 63, 837-843 (1998)
doi:10.1016/S0031-9384(97)00546-5
75. M. S. Connolly and C. B. Lynch: Classical genetic analysis of circadian body temperature rhythms in mice. Behav Genet 13, 491-500 (1983)
doi:10.1007/BF01065924
PMid:6667226
76. H. Sei, K. Oishi, Y. Morita and N. Ishida: Mouse model for morningness/eveningness. NeuroReport 12, 1461-1464 (2001)
doi:10.1097/00001756-200105250-00033
PMid:11388430
77. R. A. Irizarry, C. Tankersley, R. Frank and S. Flanders: Assessing homeostasis through circadian patterns. Biometrics 57, 1228-1237 (2001)
doi:10.1111/j.0006-341X.2001.01228.x
PMid:11764264
78. D. Weinert and J. Waterhouse: Daily activity and body temperature rhythms do not change simultaneously with age in laboratory mice. Physiol Behav 66, 605-612 (1999)
doi:10.1016/S0031-9384(98)00342-4
79. C. G. Tankersley, R. Irizarry, S. E. Flanders, R. Rabold and R. Frank: Unstable heart rate and temperature regulation predict mortality in AKR/J mice. Am J Physiol 284, R742-R750 (2003)
80. S. Nomoto, M. Ohta, S. Kanai, Y. Yoshida, S. Takiguchi, A. Funakoshi and K. Miyasaka: Absence of the cholecystokinin-A receptor deteriorates homeostasis of body temperature in response to changes in ambient temperature. Am J Physiol 287, R556-R561 (2004)
81. E. Filipski, V. M. King, M. C. Etienne, X. M. Li, B. Claustrat, T. G. Granda, G. Milano, M. H. Hastings and F. Lévi: Persistent twenty-four hour changes in liver and bone marrow despite suprachiasmatic nuclei ablation in mice. Am J Physiol 287, R844-R851 (2004)
82. E. Filipski, V. M. King, X. M. Li, T. G. Granda, M. C. Mormont, X. H. Liu, B. Claustrat, M. H. Hastings and F. Lévi: Host circadian clock as a control point in tumor progression. J Nat Cancer Inst 94, 690-697 (2002)
83. K. Nagashima, K. Matsue, M. Konishi, C. Iidaka, K. Miyazaki, N. Ishida and K. Kanosue: The involvement of Cry1 and Cry2 genes in the regulation of the circadian body temperature rhythm in mice. Am J Physiol 288, R329-R335 (2005)
84. H. Lee, T. Iida, A. Mizuno, M. Suzuki and M. J. Caterina: Altered thermal selection behavior in mice lacking transient receptor potential vanilloid 4. J Neurosci 25, 1304-1310 (2005)
doi:10.1523/JNEUROSCI.4745.04.2005
PMid:15689568
85. B. Conti, M. Sanchez-Alavez, R. Winsky-Sommerer, M. C. Morale, J. Lucero, S. Brownell, V. Fabre, S. Huitron-Resendiz, S. Henriksen, E. P. Zorrilla, L. de Lecea and T. Bartfai: Transgenic mice with a reduced core body temperature have an increased life span. Science 314, 825-828 (2006)
doi:10.1126/science.1132191
PMid:17082459
86. C. Liu, S. Li, T. Liu, J. Borjigin and J. D. Lin: Transcriptional coactivator PGC-1alpha integrates the mammalian clock and energy metabolism. Nature 447, 477-481 (2007)
doi:10.1038/nature05767
PMid:17476214
87. G. E. Folk: Twenty-four hour rhythms of mammals in a cold environment. Am Nat 91, 153-166 (1957)
doi:10.1086/281975
88. P. J. DeCoursey, S. Pius, C. Sandlin, D. Wethey and J. Schull: Relationship of circadian temperature and activity rhythms in two rodent species. Physiol Behav 65, 457-463 (1998)
doi:10.1016/S0031-9384(98)00187-5
89. C. A. Conn, K. T. Borer and M. J. Kluger: Body temperature rhythm and response to pyrogen in exercising and sedentary hamsters. Med Sci Sports Exerc 22, 636-642 (1990)
doi:10.1249/00005768-199010000-00015
90. A. P. Chaudhry, F. Halberg, C. E. Keenan, R. N. Harner and J. J. Bittner: Daily rhythms in rectal temperature and in epithelial mitoses of hamster pinna and pouch. J Appl Physiol 12, 221-224 (1958)
91. D. A. Golombek, G. Ortega and D. P. Cardinali: Wheel running raises body temperature and changes the daily cycle in golden hamsters. Physiol Behav 53, 1049-1054 (1993)
doi:10.1016/0031-9384(93)90358-M
92. R. Refinetti: Contribution of locomotor activity to the generation of the daily rhythm of body temperature in golden hamsters. Physiol Behav 56, 829-831 (1994)
doi:10.1016/0031-9384(94)90251-8
93. R. Refinetti: Rhythms of temperature selection and body temperature are out of phase in the golden hamster. Behav Neurosci 109, 523-527 (1995)
doi:10.1037/0735-7044.109.3.523
PMid:7662161
94. R. H. Watts Jr. and R. Refinetti: Circadian modulation of cold-induced thermogenesis in the golden hamster. Biol Rhythm Res 27, 87-94 (1996)
doi:10.1076/brhm.27.1.87.12937
95. C. M. Brown and R. Refinetti: Daily rhythms of metabolic heat production, body temperature, and locomotor activity in golden hamsters. J Therm Biol 21, 227-230 (1996)
doi:10.1016/0306-4565(96)00006-X
96. Z. Boulos, M. Macchi, T. A. Houpt and M. Terman: Photic entrainment in hamsters: effects of simulated twilights and nest box availability. J Biol Rhythms 11, 216-233 (1996)
doi:10.1177/074873049601100304
PMid:8872594
97. N. Kronfeld-Schor, T. Dayan, R. Elvert, A. Haim, N. Zisapel and G. Heldmaier: On the use of the time axis for ecological separation: diel rhythms as an evolutionary constraint. Am Nat 158, 451-457 (2001)
doi:10.1086/321991
PMid:18707339
98. A. Rubal, I. Choshniak and A. Haim: Daily rhythms of metabolic rate and body temperature of two murids from extremely different habitats. Chrobiol Int 9, 341-349 (1992)
doi:10.3109/07420529209064545
PMid:1394605
99. R. Elvert, N. Kronfeld, T. Dayan, A. Haim, N. Zisapel and G. Heldmaier: Telemetric field studies of body temperature and activity rhythms of Acomys russatus and A. cahirinus in the Judean Desert of Israel. Oecologia 119, 484-492 (1999)
doi:10.1007/s004420050811
100. A. Haim, I. Yedidia, D. Haim and N. Zisapel: Photoperiodicity in daily rhythms of body temperature, food and energy intake of the golden spiny mouse (Acomys russatus). Isr J Zool 40, 145-150 (1994)
101. A. Haim and N. Zisapel: Oxygen consumption and body temperature rhythms in the golden spiny mouse: responses to changes in day length. Physiol Behav 58, 775-778 (1995)
doi:10.1016/0031-9384(95)00126-4
102. B. G. Lovegrove and G. Heldmaier: The amplitude of circadian body temperature rhythms in three rodents (Aethomys namaquensis, Thallomys paedulcus and Cryptomys damarensis) along the arboreal-subterranean gradient. Aust J Zool 42, 65-78 (1994)
doi:10.1071/ZO9940065
103. A. K. Gebczynski and J. R. E. Taylor: Daily variation of body temperature, locomotor activity and maximum nonshivering thermogenesis in two species of small rodents. J Therm Biol 29, 123-131 (2004)
doi:10.1016/j.jtherbio.2004.01.001
104. A. Haim, R. M. McDevitt and J. R. Speakman: Thermoregulatory responses to manipulations of photoperiod in wood mice Apodemus sylvaticus from high latitudes. J Therm Biol 20, 437-443 (1995)
doi:10.1016/0306-4565(95)00002-E
105. T. L. McElhinny, L. Smale and K. E. Holekamp: Patterns of body temperature, activity, and reproductive behavior in a tropical murid rodent, Arvicanthis niloticus. Physiol Behav 62, 91-96 (1997)
doi:10.1016/S0031-9384(97)00146-7
106. J. A. Blanchong, T. L. McElhinny, M. M. Mahoney and L. Smale: Nocturnal and diurnal rhythms in the unstriped Nile rate, Arvicanthis niloticus. J Biol Rhythms 14, 364-377 (1999)
doi:10.1177/074873099129000777
PMid:10511004
107. M. Akita, K. Ishii, M. Kuwahara and H. Tsubone: The daily pattern of heart rate, body temperature, and locomotor activity in guinea pigs. Exp Anim 50, 409-415 (2001)
doi:10.1538/expanim.50.409
PMid:11769543
108. R. Refinetti: Body temperature and behavior of tree shrews and flying squirrels in a thermal gradient. Physiol Behav 63, 517-520 (1998)
doi:10.1016/S0031-9384(97)00485-X
109. S. R. Hayes: Daily activity and body temperature of the southern woodchuck, Marmota monax monax, in northwestern Arkansas. J Mammal 57, 291-299 (1976)
doi:10.2307/1379689
PMid:932569
110. D. Weinert, A. Nevill, R. Weinandy and J. Waterhouse: The development of new purification methods to assess the circadian rhythm of body temperature in Mongolian gerbils. Chrobiol Int 20, 249-270 (2003)
doi:10.1081/CBI-120018649
PMid:12723884
111. D. Weinert, R. Weinandy and R. Gattermann: Photic and non-photic effects on the daily activity pattern of Mongolian gerbils. Physiol Behav 90, 325-333 (2007)
doi:10.1016/j.physbeh.2006.09.019
112. S. Saarela and R. Hissa: Metabolism, thermogenesis and daily rhythm of body temperature in the wood lemming, Myopus schisticolor. J Comp Physiol B 163, 546-555 (1993)
doi:10.1007/BF00302113
113. M. J. H. Kas and D. M. Edgar: Crepuscular rhythms of EEG sleep-wake in a hystricomorph rodent, Octodon degus. J Biol Rhythms 13, 9-17 (1998)
doi:10.1177/074873098128999871
PMid:9486839
114. S. E. Labyak and T. M. Lee: Estrus- and steroid-induced changes in circadian rhythms in a diurnal rodent, Octodon degus. Physiol Behav 58, 573-585 (1995)
doi:10.1016/0031-9384(95)00096-2
115. R. Refinetti: Rhythms of body temperature and temperature selection are out of phase in a diurnal rodent, Octodon degus. Physiol Behav 60, 959-961 (1996)
116. M. J. H. Kas and D. M. Edgar: A nonphotic stimulus inverts the diurnal-nocturnal phase preference in Octodon degus. J Neurosci 19, 328-333 (1999)
117. N. Goel and T. M. Lee: Social cues accelerate reentrainment of circadian rhythms in diurnal female Octodon degus (Rodentia: Octodontidae). Chrobiol Int 12, 311-323 (1995)
doi:10.3109/07420529509057280
118. R. Refinetti: Homeostatic and circadian control of body temperature in the fat-tailed gerbil. Comp Biochem Physiol A 119, 295-300 (1998)
doi:10.1016/S1095-6433(97)00436-4
119. G. A. Sacher and P. H. Duffy: Age changes in rhythms of energy metabolism, activity, and body temperature in Mus and Peromyscus. In: Samis, H. V. & Capobianco, S. (Eds.). Aging and Biological Rhythms. New York: Plenum, pp. 105-124
120. S. Steinlechner, A. Stieglitz and T. Ruf: Djungarian hamsters: a species with a labile circadian pacemaker? Arrhythmicity under a light-dark cycle induced by short light pulses. J Biol Rhythms 17, 248-258 (2002)
121. E. Halberg, F. Halberg, R. M. Timm, P. J. Regal, P. Cugigni and P. de Remigis: Socially-related and spontaneous circadian thermo-acrophase shifts in Rhabdomys pumilio: complications for chronopharmacologists. In: Takahashi, R., Halberg, F. & Walker, C. A. (Eds.). Toward Chronopharmacology. Oxford, UK: Pergamon, pp. 357-368
122. A. Haim, G. T. H. Ellison and J. D. Skinner: Thermoregulatory circadian rhythms in the pouched mouse (Saccostomus campestris). Comp Biochem Physiol A 91, 123-127 (1988)
doi:10.1016/0300-9629(88)91603-9
123. A. Haim: Food and energy intake, non-shivering thermogenesis and daily rhythm of body temperature in the bushy-tailed gerbil Sekeetamys calurus: the role of photoperiod manipulations. J Therm Biol 21, 37-42 (1996)
doi:10.1016/0306-4565(96)81275-7
124. B. D. Goldman, S. L. Goldman, A. P. Riccio and J. Terkel: Circadian patterns of locomotor activity and body temperature in blind mole-rats, Spalax ehrenbergi. J Biol Rhythms 12, 348-361 (1997)
doi:10.1177/074873049701200407
PMid:9438883
125. A. E. Muchlinski, B. C. Baldwin, D. A. Padick, B. Y. Lee, H. S. Salguero and R. Gramajo: California ground squirrel body temperature regulation patterns measured in the laboratory and in the natural environment. Comp Biochem Physiol A 120, 365-372 (1998)
doi:10.1016/S1095-6433(98)10037-5
126. T. M. Lee, W. G. Holmes and I. Zucker: Temperature dependence of circadian rhythms in golden-mantled ground squirrels. J Biol Rhythms 5, 25-34 (1990)
doi:10.1177/074873049000500103
PMid:2133117
127. R. Refinetti: Body temperature and behaviour of golden hamsters (Mesocricetus auratus) and ground squirrels (Spermophilus tridecemlineatus) in a thermal gradient. J Comp Physiol A 177, 701-705 (1995)
doi:10.1007/BF00187629
128. R. Refinetti: The body temperature rhythm of the thirteen-lined ground squirrel, Spermophilus tridecemlineatus. Physiol Zool 69, 270-275 (1996)
129. A. Haim, C. T. Downs and J. Raman: Effects of adrenergic blockade on the daily rhythms of body temperature and oxygen consumption of the black-tailed tree rat (Thallomys nigricauda) maintained under different photoperiods. J Therm Biol 26, 171-177 (2001)
doi:10.1016/S0306-4565(00)00039-5
PMid:11240222
130. H. G. Erkert and B. Cramer: Chronobiological background to cathemerality: circadian rhythms in Eulemur fulvus albifrons (Prosimii) and Aotus azarai boliviensis (Anthropoidea). Folia Primatol 77, 87-103 (2006)
doi:10.1159/000089697
131. T. M. Hoban, A. H. Levine, R. B. Shane and F. M. Sulzman: Circadian rhythms of drinking and body temperature of the owl monkey (Aotus trivirgatus). Physiol Behav 34, 513-518 (1985)
doi:10.1016/0031-9384(85)90042-3
132. C. M. Winget, D. H. Card and N. W. Hetherington: Circadian oscillations of deep-body temperature and heart rate in a primate (Cebus albafrons). Aerosp Med 39, 350-353 (1968)
133. N. Takasu, H. Nigi and H. Tokura: Effects of diurnal bright/dim light intensity on circadian core temperature and activity rhythms in the Japanese macaque. Jap J Physiol 52, 573-578 (2002)
doi:10.2170/jjphysiol.52.573
PMid:12617763
134. S. Simpson and J. J. Galbraith: Observations on the normal temperature of the monkey and its diurnal variation, and on the effect of changes in the daily routine on this variation. Trans R Soc Edinb 45, 65-104 (1906)
135. W. N. Tapp and B. H. Natelson: Circadian rhythms and patterns of performance before and after simulated jet lag. Am J Physiol 257, R796-R803 (1989)
136. F. Génin and M. Perret: Daily hypothermia in captive grey mouse lemurs (Microcebus murinus): effects of photoperiod and food restriction. Comp Biochem Physiol B 136, 71-81 (2003)
doi:10.1016/S1096-4959(03)00172-6
137. F. Aujard and F. Vasseur: Effect of ambient temperature on the body temperature rhythm of male gray mouse lemurs (Microcebus murinus). Int J Primatol 22, 43-56 (2001)
doi:10.1023/A:1026461914534
138. M. Perret and F. Aujard: Daily hypothermia and torpor in a tropical primate: synchronization by 24-h light-dark cycle. Am J Physiol 281, R1925-R1933 (2001)
139. M. Perret, F. Aujard, M. Séguy and A. Schilling: Olfactory bulbectomy modifies photic entrainment and circadian rhythms of body temperature and locomotor activity in a nocturnal primate. J Biol Rhythms 18, 392-401 (2003)
doi:10.1177/0748730403254248
PMid:14582855
140. C. A. Fuller: Circadian brain and body temperature rhythms in the squirrel monkey. Am J Physiol 246, R242-R246 (1984)
141. C. A. Fuller, F. M. Sulzman and M. C. Moore-Ede: Role of heat loss and heat production in generation of the circadian temperature rhythm of the squirrel monkey. Physiol Behav 34, 543-546 (1985)
doi:10.1016/0031-9384(85)90046-0
142. M. C. Moore-Ede, D. A. Kass and J. A. Herd: Transient circadian internal desynchronization after light-dark phase shift in monkeys. Am J Physiol 232, R31-R37 (1977)
143. C. A. Fuller, F. M. Sulzman and M. C. Moore-Ede: Thermoregulation is impaired in an environment without circadian time cues. Science 199, 794-796 (1978)
doi:10.1126/science.414356
PMid:414356
144. C. A. Fuller and D. M. Edgar: Effects of light intensity on the circadian temperature and feeding rhythms in the squirrel monkey. Physiol Behav 36, 687-691 (1986)
doi:10.1016/0031-9384(86)90355-0
145. F. M. Sulzman, C. A. Fuller and M. C. Moore-Ede: Feeding time synchronizes primate circadian rhythms. Physiol Behav 18, 775-779 (1977)
doi:10.1016/0031-9384(77)90182-2
146. J. Aschoff, U. Gerecke and R. Wever: Desynchronization of human circadian rhythms. Jap J Physiol 17, 450-457 (1967)
147. R. Wever and R. A. Zink: Fortlaufende Registrierung der Rectaltemperatur des Menschen unter extremen Bedingungen. Pflügers Arch 327, 186-190 (1971)
doi:10.1007/BF00587369
PMid:5105593
148. L. A. Stephenson, C. B. Wenger, B. H. O'Donovan and E. R. Nadel: Circadian rhythm in sweating and cutaneous blood flow. Am J Physiol 246, R321-R324 (1984)
149. G. W. G. Sharp: Reversal of diurnal temperature rhythms in man. Nature 190, 146-148 (1961)
doi:10.1038/190146a0
150. F. G. Benedict: Studies in body temperature. I. Influence of the inversion of the daily routine; the temperature of night-workers. Am J Physiol 11, 145-169 (1904)
151. K. A. Lee: Circadian temperature rhythms in relation to menstrual cycle phase. J Biol Rhythms 3, 255-263 (1988)
doi:10.1177/074873048800300304
152. H. C. Mellette, B. K. Hutt, S. I. Askovitz and S. M. Horvath: Diurnal variations in body temperature. J Appl Physiol 3, 665-675 (1951)
153. T. Tsujimoto, N. Yamada, K. Shimoda, K. Hanada and S. Takahashi: Circadian rhythms in depression. Part I: Monitoring of the circadian body temperature rhythm. J Affect Disord 18, 193-197 (1990)
doi:10.1016/0165-0327(90)90036-8
PMid:2139064
154. E. Souetre, E. Salvati, T. A. Wehr, D. A. Sack, B. Krebs and G. Darcourt: Twenty-four-hour profiles of body temperature and plasma TSH in bipolar patients during depression and during remission and in normal control subjects. Am J Psychiatry 145, 1133-1137 (1988)
155. W. E. Scales, A. J. Vander, M. B. Brown and M. J. Kluger: Human circadian rhythms in temperature, trace metals, and blood variables. J Appl Physiol 65, 1840-1846 (1988)
156. H. Marotte and J. Timbal: Circadian rhythm of temperature in man: comparative study with two experiment protocols. Chronobiologia 8, 87-100 (1981)
157. A. L. Elliott, J. N. Mills, D. S. Minors and J. M. Waterhouse: The effect of real and simulated time-zone shifts upon the circadian rhythms of body temperature, plasma 11-hydroxycorticosteroids, and renal excretion in human subjects. J Physiol Lond 221, 227-257 (1972)
158. P. H. Gander, L. J. Connell and R. C. Graeber: Masking of the circadian rhythm of heart rate and core temperature by the rest-activity cycle in man. J Biol Rhythms 1, 119-135 (1986)
doi:10.1177/074873048600100203
PMid:2979578
159. J. Aschoff, U. Gerecke and R. Wever: Phasenbeziehungen zwischen den circadianen Perioden der Aktivität und der Kerntemperatur beim Menschen. Pflügers Arch 295, 173-183 (1967)
doi:10.1007/BF00362748
160. C. A. Czeisler, R. E. Kronauer, J. S. Allan, J. F. Duffy, M. E. Jewett, E. N. Brown and J. M. Ronda: Bright light induction of strong (Type 0) resetting of the human circadian pacemaker. Science 244, 1328-1333 (1989)
doi:10.1126/science.2734611
PMid:2734611
161. J. Kriebel: Changes in internal phase relationships during isolation. In: Scheving, L. E., Halberg, F. & Pauly, J. E. (Eds.). Chronobiology. Tokyo: Igaku Shoin, pp. 451-459
162. E. D. Weitzman, M. L. Moline, C. A. Czeisler and J. C. Zimmerman: Chronobiology of aging: temperature, sleep-wake rhythms and entrainment. Neurobiol Aging 3, 299-309 (1982)
doi:10.1016/0197-4580(82)90018-5
PMid:7170047
163. Y. Nakazawa, K. Nonaka, N. Nishida, N. Hayashida, Y. Miyahara, T. Kotorii and K. Matsuoka: Comparison of body temperature rhythms between healthy elderly and healthy young adults. Jap J Psychiatry Neurol 45, 37-43 (1991)
164. N. Kleitman and A. Ramsaroop: Periodicity in body temperature and heart rate. Endocrinology 43, 1-20 (1948)
doi:10.1210/endo-43-1-1
PMid:18871457
165. F. Cisse, R. Martineaud and J. P. Martineaud: Circadian cycles of central temperature in hot climate in man. Arch Int Physiol Biochim Biophys 99, 155-159 (1991)
doi:10.3109/13813459109146956
166. M. C. Lobban: The entrainment of circadian rhythms in man. Cold Spring Harb Symp Quant Biol 25, 325-332 (1960)
167. T. L. Shanahan and C. A. Czeisler: Light exposure induces equivalent phase shifts of the endogenous circadian rhythms of circulating plasma melatonin and core body temperature in men. J Clin Endocrinol Metabol 73, 227-235 (1991)
doi:10.1210/jcem-73-2-227
168. K. Honma, S. Honma, M. Kohsaka and N. Fukuda: Seasonal variation in the human circadian rhythm: dissociation between sleep and temperature rhythm. Am J Physiol 262, R885-R891 (1992)
169. J. Barrett, L. Lack and M. Morris: The sleep-evoked decrease of body temperature. Sleep 16, 93-99 (1993)
170. Y. H. Lee and H. Tokura: Circadian rhythm of human rectal and skin temperatures under the influences of three different kinds of clothing. J Interdiscipl Cycle Res 24, 33-42 (1993)
171. C. P. Pollak and D. R. Wagner: Core body temperature in narcoleptic and normal subjects living in temporal isolation. Pharmacol Biochem Behav 47, 65-71 (1994)
doi:10.1016/0091-3057(94)90112-0
172. K. Kräuchi and A. Wirz-Justice: Circadian rhythm of heat production, heart rate, and skin and core temperature under unmasking conditions in men. Am J Physiol 267, R819-R829 (1994)
173. K. Honma, S. Honma, K. Nakamura, M. Sasaki, T. Endo and T. Takahashi: Differential effects of bright light and social cues on reentrainment of human circadian rhythms. Am J Physiol 268, R528-R535 (1995)
174. H. P. A. Van Dongen, G. A. Kerkhof and J. H. M. Souverijn: Absence of seasonal variation in the phase of the endogenous circadian rhythm in humans. Chrobiol Int 15, 623-632 (1998)
doi:10.3109/07420529808993198
PMid:9844750
175. R. Leproult, O. Van Reeth, M. M. Byrne, J. Sturis and E. Van Cauter: Sleepiness, performance, and neuroendocrine function during sleep deprivation: effects of exposure to bright light or exercise. J Biol Rhythms 12, 245-258 (1997)
doi:10.1177/074873049701200306
PMid:9181436
176. D. Callard, D. Davenne, D. Lagarde, I. Meney, C. Gentil and J. Van Hoecke: Nycthemeral variations in core temperature and heart rate: continuous cycling exercise versus continuous rest. Int J Sports Med 22, 553-557 (2001)
doi:10.1055/s-2001-18524
PMid:11719889
177. D. J. Dijk, D. F. Neri, J. K. Wyatt, J. M. Ronda, E. Riel, A. R. de Cecco, R. J. Hughes, A. R. Elliott, G. K. Prisk, J. B. West and C. A. Czeisler: Sleep, performance, circadian rhythms, and light-dark cycles during two space shuttle flights. Am J Physiol 281, R1647-R1664 (2001)
178. C. M. Spengler, C. A. Czeisler and S. A. Shea: An endogenous circadian rhythm of respiratory control in humans. J Physiol Lond 526, 683-694 (2000)
doi:10.1111/j.1469-7793.2000.00683.x
PMid:10922018 PMCid:2270042
179. S. Moussay, F. Dosseville, A. Gauthier, J. Larue, B. Sesboüe and D. Davenne: Circadian rhythms during cycling exercise and finger-tapping task. Chrobiol Int 19, 1137-1149 (2002)
doi:10.1081/CBI-120015966
PMid:12511031
180. G. Murray, N. B. Allen and J. Trinder: Mood and the circadian system: investigation of a circadian component in positive affect. Chrobiol Int 19, 1151-1169 (2002)
doi:10.1081/CBI-120015956
PMid:12511032
181. A. Cagnacci, S. Arangino, F. Tuveri, A. M. Paoletti and A. Volpe: Regulation of the 24-h body temperature rhythm of women in luteal phase: role of gonadal steroids and prostaglandins. Chrobiol Int 19, 721-730 (2002)
doi:10.1081/CBI-120005394
PMid:12182499
182. M. Varkevisser and G. A. Kerkhof: 24-Hour assessment of performance on a palmtop computer: validating a self-constructed test battery. Chrobiol Int 20, 109-121 (2003)
doi:10.1081/CBI-120017685
PMid:12638694
183. M. Gradisar and L. Lack: Relationships between the circadian rhythms of finger temperature, core temperature, sleep latency, and subjective sleepiness. J Biol Rhythms 19, 157-163 (2004)
doi:10.1177/0748730403261560
PMid:15038855
184. D. Bratzke, B. Rolke, R. Ulrich and M. Peters: Central slowing during the night. Psychol Sci 18, 456-461 (2007)
doi:10.1111/j.1467-9280.2007.01921.x
PMid:17576287
185. R. O. Rawson, J. A. J. Stolwijk, H. Graichen and R. Abrams: Continuous radio telemetry of hypothalamic temperatures from unrestrained animals. J Appl Physiol 20, 321-325 (1965)
186. F. Hawking, M. C. Lobban, K. Gammage and M. J. Worms: Circadian rhythms (activity, temperature, urine and microfilariae) in dog, cat, hen, duck, Thamnomys and Gerbillus. J Interdiscipl Cycle Res 2, 455-473 (1971)
187. R. Refinetti and G. Piccione: Daily rhythmicity of body temperature in the dog. J Vet Med Sci 65, 935-937 (2003)
doi:10.1292/jvms.65.935
PMid:12951430
188. G. Piccione, G. Caola and R. Refinetti: Daily rhythms of blood pressure, heart rate, and body temperature in fed and fasted male dogs. J Vet Med A 52, 377-381 (2005)
doi:10.1111/j.1439-0442.2005.00758.x
PMid:16176564
189. N. Kuwabara, K. Seki and K. Aoki: Circadian, sleep and brain temperature rhythms in cats under sustained daily light-dark cycles and constant darkness. Physiol Behav 38, 283-289 (1986)
doi:10.1016/0031-9384(86)90164-2
190. R. F. Johnson and W. Randall: Freerunning and entrained circadian rhythms in body temperature in the domestic cat. J Interdiscipl Cycle Res 16, 49-61 (1985)
191. W. Randall, J. T. Cunningham, S. Randall, J. Liittschwager, and R. F. Johnson: A two-peak circadian system in body temperature and activity in the domestic cat, Felis catus. J Therm Biol 12, 27-37 (1987)
doi:10.1016/0306-4565(87)90020-9
192. C. Jessen, R. Dmi'el, I. Choshniak, D. Ezra and G. Kuhnen: Effects of dehydration and rehydration on body temperatures in the black Bedouin goat. Pflügers Arch 436, 659-666 (1998)
doi:10.1007/s004240050686
PMid:9716697
193. J. O. Ayo, S. B. Oladele, S. Ngam, A. Fayomi and S. B. Afolayan: Diurnal fluctuations in rectal temperature of the Red Sokoto goat during the harmattan season. Res Vet Sci 66, 7-9 (1998)
doi:10.1053/rvsc.1998.0231
PMid:10088705
194. G. Piccione, G. Caola and R. Refinetti: Circadian rhythms of body temperature and liver function in fed and food-deprived goats. Comp Biochem Physiol A 134, 563-572 (2003)
doi:10.1016/S1095-6433(02)00362-8
195. C. Jessen and G. Kuhnen: Seasonal variations of body temperature in goats living in an outdoor environment. J Therm Biol 21, 197-204 (1996)
doi:10.1016/0306-4565(96)00004-6
196. N. R. Mphahlele, A. Fuller, J. Roth and P. R. Kamerman: Body temperature, behavior, and plasma cortisol changes induced by chronic infusion of Staphylococcus aureus in goats. Am J Physiol 287, R863-R869 (2004)
197. E. G. Mohr and H. Krzywanek: Endogenous oscillator and regulatory mechanisms of body temperature in sheep. Physiol Behav 57, 339-347 (1995)
doi:10.1016/0031-9384(94)00273-8
198. S. E. Recabarren, M. Vergara, A. J. Llanos and M. Serón-Ferré: Circadian variation of rectal temperature in newborn sheep. J Devl Physiol 9, 399-408 (1987)
199. J. Bligh, D. L. Ingram, R. D. Keynes and S. G. Robinson: The deep body temperature of an unrestrained Welsh mountain sheep recorded by a radiotelemetric technique during a 12-month period. J Physiol Lond 176, 136-144 (1965)
200. E. Mohr and H. Krzywanek: Variations of core-temperature rhythms in unrestrained sheep. Physiol Behav 48, 467-473 (1990)
doi:10.1016/0031-9384(90)90345-5
201. T. E. Lowe, C. J. Cook, Ingram. J. R. and P. J. Harris: Impact of climate on thermal rhythm in pastoral sheep. Physiol Behav 74, 659-664 (2001)
doi:10.1016/S0031-9384(01)00608-4
202. G. Piccione, G. Caola and R. Refinetti: Circadian modulation of starvation-induced hypothermia in sheep and goats. Chrobiol Int 19, 531-541 (2002)
doi:10.1081/CBI-120004225
PMid:12069036
203. G. Piccione, G. Caola and R. Refinetti: Temporal relationships of 21 physiological variables in horse and sheep. Comp Biochem Physiol A 142, 389-396 (2005)
doi:10.1016/j.cbpa.2005.07.019
204. G. Piccione, G. Caola and R. Refinetti: Feeble weekly rhythmicity in hematological, cardiovascular, and thermal parameters in the horse. Chrobiol Int 21, 571-589 (2004)
doi:10.1081/CBI-200026447
PMid:15470955
205. G. Piccione, G. Caola and R. Refinetti: The circadian rhythm of body temperature of the horse. Biol Rhythm Res 33, 113-119 (2002)
doi:10.1076/brhm.33.1.113.1322
206. R. Refinetti and G. Piccione: Intra- and inter-individual variability in the circadian rhythm of body temperature of rats, squirrels, dogs, and horses. J Therm Biol 30, 139-146 (2005)
doi:10.1016/j.jtherbio.2004.09.003
207. A. R. Green, R. S. Gates and L. M. Lawrence: Measurement of horse core body temperature. J Therm Biol 30, 370-377 (2005)
doi:10.1016/j.jtherbio.2005.03.003
208. J. E. Smith, A. L. Barnes and S. K. Maloney: A nonsurgical method allowing continuous core temperature monitoring in mares for extended periods, including during endurance exercise. Equine Vet J Suppl 36, 65-69 (2006)
209. G. Piccione, G. Caola and R. Refinetti: Daily and estrous rhythmicity of body temperature in domestic cattle. BMC Physiol 3, art. 7 (2003)
210. A. M. Lefcourt, J. B. Huntington, R. M. Akers, D. L. Wood and J. Bitman: Circadian and ultradian rhythms of body temperature and peripheral concentrations of insulin and nitrogen in lactating dairy cows. Domest Anim Endocrinol 16, 41-55 (1999)
doi:10.1016/S0739-7240(98)00047-2
PMid:10081662
211. G. L. Hahn, R. A. Eigenberg, J. A. Nienaber and E. T. Littledike: Measuring physiological responses of animals to environmental stressors using a microcomputer-based portable datalogger. J Anim Sci 68, 2658-2665 (1990)
212. C. T. Araki, R. M. Nakamura, and L. W. G. Kam: Diurnal temperature sensitivity of dairy cattle in a naturally cycling environment. J Therm Biol 12, 23-26 (1987)
doi:10.1016/0306-4565(87)90019-2
213. G. L. Hahn, Y. R. Chen, J. A. Nienaber, R. A. Eigenberg and A. M. Parkhurst: Characterizing animal stress through fractal analysis of thermoregulatory responses. J Therm Biol 17, 115-120 (1992)
doi:10.1016/0306-4565(92)90008-4
214. G. Körtner and F. Geiser: Body temperature rhythms and activity in reproductive Antechinus (Marsupialia). Physiol Behav 58, 31-36 (1995)
doi:10.1016/0031-9384(94)00384-H
215. R. W. Rose, R. Swain and S. L. Bryant: Body temperature: rhythm and regulation in the Tasmanian bettong (Bettongia gaimardi) (Marsupialia: Potoroidae). Comp Biochem Physiol A 97, 573-576 (1990)
doi:10.1016/0300-9629(90)90130-K
216. E. B. Bakko, W. P. Porter and B. A. Wunder: Body temperature patterns in black-tailed prairie dogs in the field. Can J Zool 66, 1783-1789 (1988)
doi:10.1139/z88-258
217. H. J. Harlow, J. A. Phillips and C. L. Ralph: Circadian rhythms and the effects of exogenous melatonin in the nine-banded armadillo, Dasypus novemcinctus: a mammal lacking a distinct pineal gland. Physiol Behav 29, 307-313 (1982)
doi:10.1016/0031-9384(82)90020-8
218. R. T. Gemmell, S. J. Turner and W. J. Krause: The circadian rhythm of body temperature of four marsupials. J Therm Biol 22, 301-307 (1997)
doi:10.1016/S0306-4565(97)00026-0
219. P. A. Fowler and P. A. Racey: Daily and seasonal cycles of body temperature and aspects of heterothermy in the hedgehog Erinaceus europaeus. J Comp Physiol B 160, 299-307 (1990)
doi:10.1007/BF00302596
220. A. P. Riccio and B. D. Goldman: Circadian rhythms of body temperature and metabolic rate in naked mole-rats. Physiol Behav 71, 15-22 (2000)
doi:10.1016/S0031-9384(00)00280-8
221. R. T. Wells: Thermoregulation and activity rhythms in the hairy-nosed wombat, Lasiorhinus latifrons (Owen), (Vombatidae). Aust J Zool 26, 639-651 (1978)
doi:10.1071/ZO9780639
222. H. C. K. McCarron, R. Buffenstein, F. D. Fanning and T Dawson, : Free-ranging heart rate, body temperature and energy metabolism in eastern grey kangaroos (Macropus giganteus) and red kangaroos (Macropus rufus) in the arid regions of South East Australia. J Comp Physiol B 171, 401-411 (2001)
doi:10.1007/s003600100189
223. C. E. Cooper and P. C. Withers: Patterns of body temperature variation and torpor in the numbat, Myrmecobius fasciatus (Marsupialia: Myrmecobiidae). J Therm Biol 29, 277-284 (2004)
doi:10.1016/j.jtherbio.2004.05.003
224. M. C. Chevillard-Hugot, E. F. Müller and E. Kulzer: Oxygen consumption, body temperature and heart rate in the coati (Nasua nasua). Comp Biochem Physiol A 65, 305-309 (1980)
doi:10.1016/0300-9629(80)90033-X
225. S. M. Varosi, R. L. Brigmon and E. L. Besch: A simplified telemetry system for monitoring body temperature in small animals. Lab Anim Sci 40, 299-302 (1990)
226. N. Christian and F. Geiser: To use or not to use torpor? Activity and body temperature predictors. Naturwissenschaften 94, 483-487 (2007)
doi:10.1007/s00114-007-0215-5
PMid:17252241
227. M. E. Jones, G. C. Grigg and L. A. Beard: Body temperatures and activity patterns of Tasmanian devils (Sarcophilus harrisii) and eastern quolls (Dasyurus viverrinus) through a subalpine winter. Physiol Zool 70, 53-60 (1997)
228. K. Ishii, M. Uchino, M. Kuwahara, H. Tsubone and S. Ebukuro: Diurnal fluctuations of heart rate, body temperature and locomotor activity in the house musk shrew (Suncus murinus). Exp Anim 51, 57-62 (2002)
doi:10.1538/expanim.51.57
PMid:11871153
229. M. Macari: Efeito do cruzamento de suínos sobre o comportamento termoregulador. Ciênc Cult 35, 1145-1150 (1983)
230. D. L. Ingram and L. E. Mount: The effects of food intake and fasting on 24-hourly variations in body temperature in the young pig. Pflügers Arch 339, 299-304 (1973)
doi:10.1007/BF00594165
PMid:4735611
231. J. Bligh and A. M. Harthoorn: Continuous radiotelemetric records of the deep body temperature of some unrestrained African mammals under near-natural conditions. J Physiol Lond 176, 145-162 (1965)
232. G. Hildwein and C. Kayser: Relation entre la température colonique et la consommation d'oxygène d'un insectivore, le Tenrec, au cours du nycthémère. C R Séanc Soc Biol Strasb 164, 429-432 (1970)
233. R. Refinetti and M. Menaker: Body temperature rhythm of the tree shrew, Tupaia belangeri. J Exp Zool 263, 453-457 (1992)
doi:10.1002/jez.1402630413
PMid:1402741
234. D. G. Peters and R. W. Rose: The oestrous cycle and basal body temperature in the common wombat (Vombatus ursinus). J Reprod Fert 57, 453-460 (1979)
doi:10.1530/jrf.0.0570453
235. M. E. Rashotte and D. Henderson: Coping with rising food costs in a closed economy: feeding behavior and nocturnal hypothermia in pigeons. J Exp Anal Behav 50, 441-456 (1988)
doi:10.1901/jeab.1988.50-441
PMid:3209959 PMCid:1338909
236. I. Oshima and S. Ebihara: The measurement and analysis of circadian locomotor activity and body temperature rhythms by a computer-based system. Physiol Behav 43, 115-119 (1988)
doi:10.1016/0031-9384(88)90106-0
237. M. E. Rashotte, I. F. Pastukhov, E. L. Poliakov and R. P. Henderson: Vigilance states and body temperature during the circadian cycle in fed and fasted pigeons (Columbia livia). Am J Physiol 275, R1690-R1702 (1998)
238. R. Graf: Diurnal changes of thermoregulatory functions in pigeons. I. Effector mechanisms. Pflügers Arch 386, 173-179 (1980)
doi:10.1007/BF00584205
PMid:7191971
239. I. Oshima, H. Yamada, M. Goto, K. Sato and S. Ebihara: Pineal and retinal melatonin is involved in the control of circadian locomotor activity and body temperature rhythms in the pigeon. J Comp Physiol A 166, 217-226 (1989)
doi:10.1007/BF00193466
240. B. D. Zivkovic, H. Underwood and T. Siopes: Circadian ovulatory rhythms in Japanese quail: role of ocular and extraocular pacemakers. J Biol Rhythms 15, 172-183 (2000)
doi:10.1177/074873040001500211
PMid:10762035
241. H. Underwood and K. Edmonds: The circadian rhythm of thermoregulation in Japanese quail. II. Multioscillator control. J Biol Rhythms 10, 234-247 (1995)
doi:10.1177/074873049501000306
PMid:7488761
242. H. Kadono, E. L. Besch and E. Usami: Body temperature, oviposition, and food intake in the hen during continuous light. J Appl Physiol 51, 1145-1149 (1981)
243. L. W. Bobr and B. L. Sheldon: Analysis of ovulation-oviposition patterns in the domestic fowl by telemetry measurement of deep body temperature. Aust J Biol Sci 30, 243-257 (1977)
244. H. Kadono and E. L. Besch: Influence of laying cycle on body temperature rhythm in the domestic hen. In: Tanabe, Y. (Ed.). Biological Rhythms in Birds: Neural and Endocrine Aspects. Berlin: Springer, pp. 91-99
245. H. R. Wilson, F. B. Mather, R. L. Brigmon, E. L. Besch, V. P. Dugan and N. Z. Boulos: Feeding time and body temperature interactions in broiler breeders. Poultry Sci 68, 608-616 (1989)
246. C. M. Winget and D. H. Card: Daily rhythm changes associated with variations in light intensity and color. Life Sci Space Res 5, 148-158 (1967)
247. R. J. Berger and N. H. Phillips: Constant light suppresses sleep and circadian rhythms in pigeons without consequent sleep rebound in darkness. Am J Physiol 267, R945-R952 (1994)
248. J. Aschoff and U. von Saint Paul: Brain temperature as related to gross motor activity in the unanesthetized chicken. Physiol Behav 10, 529-533 (1973)
doi:10.1016/0031-9384(73)90216-3
249. H. Michels, M. Herremans, and E. Decuypere: Light-dark variations of oxygen consumption and subcutaneous temperature in young Gallus domesticus: influence of ambient temperature and depilation. J Therm Biol 10, 13-20 (1985)
doi:10.1016/0306-4565(85)90005-1
250. J. Yang, J. L. M. Morgan, J. D. Kirby, D. W. Long and W. L. Bacon: Circadian rhythm of the preovulatory surge of luteinizing hormone and its relationships to rhythms of body temperature and locomotor activity in turkey hens. Biol Reprod 62, 1452-1458 (2000)
doi:10.1095/biolreprod62.5.1452
PMid:10775200
251. A. Fuller, P. R. Kamerman, S. K. Maloney, G. Mitchell and D. Mitchell: Variability in brain and arterial blood temperatures in free-ranging ostriches in their natural habitat. J Exp Biol 206, 1171-1181 (2003)
doi:10.1242/jeb.00230
PMid:12604577
252. L. Warnecke, P. C. Withers, E. Schleucher and S. K. Maloney: Body temperature variation of free-ranging and captive southern brown bandicoots Isoodon obesulus (Marsupialia: Paramelidae). J Therm Biol 32, 72-77 (2007)
doi:10.1016/j.jtherbio.2006.10.003
253. R. C. Taylor: Thermal preference and temporal distribution in three crayfish species. Comp Biochem Physiol A 77, 513-517 (1984)
doi:10.1016/0300-9629(84)90220-2
254. L. I. Crawshaw: Temperature selection and activity in the crayfish, Orconectes immunis. J Comp Physiol 95, 315-322 (1971)
doi:10.1007/BF00609704
255. E. Díaz-Iglesias, F. Díaz-Herrera, A. D. Re-Araujo, M. Báez-Hidalgo, M. López-Zenteno, G. Valdés-Sáanchez and A. K. López-Murillo: Temperatura preferida y consumo de oxígeno circadiano de la langosta roja, Panulirus interruptus (Randall, 1842). Cienc Mar 30, 169-178 (2004)
256. L. F. Bückle-Ramírez, F. Díaz-Herrera, F. Correa-Sandoval, B. Barón-Sevilla and M. Hernández-Rodríguez: Diel thermoregulation of the crawfish Procambarus clarkii (Crustacea: Cambaridae). J Therm Biol 19, 419-422 (1994)
doi:10.1016/0306-4565(94)90041-8
257. W Neill, Magnuson H., J. J. and G. G. Chipman: Behavioral thermoregulation by fishes: a new experimental approach. Science 176, 1443-1445 (1972)
doi:10.1126/science.176.4042.1443
PMid:17834654
258. T. L. Beitinger and J. J. Magnuson: Influence of social rank and size on thermoselection behavior of bluegill (Lepomis macrochirus). J Fish Res Board Can 32, 2133-2136 (1975)
259. W. W. Reynolds, M. E. Casterlin, J. K. Matthey, S. T. Millington and A. C. Ostrowski: Diel patterns of preferred temperature and locomotor activity in the goldfish Carassius auratus. Comp Biochem Physiol A 59, 225-227 (1978)
doi:10.1016/0300-9629(78)90211-6
260. M. Kavaliers and C. L. Ralph: Pineal involvement in the control of behavioral thermoregulation of the white sucker, Catostomus commersoni. J Exp Zool 212, 301-303 (1980)
doi:10.1002/jez.1402120216
261. H. Schurmann and J. S. Christiansen: Behavioral thermoregulation and swimming activity of two arctic teleosts (subfamily Gadinae): the Polar cod (Boreogadus saida) and the navaga (Eleginus navaga). J Therm Biol 19, 207-212 (1994)
doi:10.1016/0306-4565(94)90032-9
262. A. Innicenti, L. Minutini and A. Foà: The pineal and circadian rhythms of temperature selection and locomotion in lizards. Physiol Behav 53, 911-915 (1993)
doi:10.1016/0031-9384(93)90268-K
263. G. Tosini and M. Menaker: The pineal complex and melatonin affect the expression of the daily rhythm of behavioral thermoregulation in the green iguana. J Comp Physiol A 179, 135-142 (1996)
doi:10.1007/BF00193441
264. L. M. Sievert and V. H. Hutchison: Light versus heat: thermoregulatory behavior in a nocturnal lizard (Gekko gecko). Herpetologica 44, 266-273 (1988)
265. R. P. Brown: Thermal biology of the gecko Tarentola boettgeri: comparisons among populations from different elevations within Gran Canaria. Herpetologica 52, 396-405 (1996)
266. P. J. Regal: Voluntary hypothermia in reptiles. Science 155, 1551-1553 (1967)
doi:10.1126/science.155.3769.1551
PMid:6020475
267. J. Cowgell and H. Underwood: Behavioral thermoregulation in lizards: a circadian rhythm. J Exp Zool 210, 189-194 (1979)
doi:10.1002/jez.1402100122
268. P. D. Rismiller and G. Heldmaier: Seasonal changes in daily metabolic patterns of Lacerta viridis. J Comp Physiol B 161, 482-488 (1991)
doi:10.1007/BF00257903
269. R. Refinetti and S. J. Susalka: Circadian rhythm of temperature selection in a nocturnal lizard. Physiol Behav 62, 331-336 (1997)
doi:10.1016/S0031-9384(97)88989-5
270. K. A. Christian, C. R. Tracy, and W. P. Porter: Inter- and intra-individual variation in body temperatures of the Galapagos land iguana (Conolophus pallidus). J Therm Biol 10, 47-50 (1985)
doi:10.1016/0306-4565(85)90010-5
271. L. M. Sievert and V. H. Hutchison: Influences of season, time of day, light and sex on the thermoregulatory behaviour of Crotaphytus collaris. J Therm Biol 14, 159-165 (1989)
doi:10.1016/0306-4565(89)90039-9
272. C. Jarling, M. Scarperi, and A. Bleichert: Circadian rhythm in the temperature preference of the turtle, Chrysemys scripta elegans, in a thermal gradient. J Therm Biol 14, 173-178 (1989)
doi:10.1016/0306-4565(89)90001-6
273. R. Shine and R. Lambeck: Seasonal shifts in the thermoregulatory behaviour of Australian blacksnakes, Pseudechis porphyriacus (Serpentes: Elapidae). J Therm Biol 15, 301-305 (1990)
doi:10.1016/0306-4565(90)90016-B
274. D. C. Skinner: Effect of intraperitoneal melatonin injections on thermoregulation in the Transvaal girdled lizard, Cordylus vittifer. J Therm Biol 16, 179-184 (1991)
doi:10.1016/0306-4565(91)90041-Y
275. L. M. Sievert and M. A. Paulissen: Temperature selection and thermoregulatory precision of bisexual and parthenogenetic Cnemidophorus lizards from southern Texas. J Therm Biol 21, 15-20 (1996)
doi:10.1016/0306-4565(95)00018-6
276. G. Tosini and M. Menaker: Multioscillatory circadian organization in a vertebrate, Iguana iguana. J Neurosci 18, 1105-1114 (1998)
277. G. Tosini and M. Menaker: Circadian rhythm of body temperature in an ectotherm (Iguana iguana). J Biol Rhythms 10, 248-255 (1995)
doi:10.1177/074873049501000307
PMid:7488762
278. F. Kronenberg and H. C. Heller: Colonial thermoregulation in honey bees (Apis mellifera). J Comp Physiol 148, 65-76 (1982)
279. S. Barassin, M. Saboureau, A. Kalsbeek, B. Bothorel, B. Vivien-Roels, A. Buijs Malan, Guardiola-Lemaitre R. M., B. and P. Pévet: Interindividual differences in the pattern of melatonin secretion of the Wistar rat. J Pineal Res 27, 193-201 (1999)
doi:10.1111/j.1600-079X.1999.tb00615.x
PMid:10551766
280. B. Selmaoui and Y. Touitou: Reproducibility of the circadian rhythms of serum cortisol and melatonin in healthy subjects: a study of three different 24-h cycles over six weeks. Life Sci 73, 3339-3349 (2003)
doi:10.1016/j.lfs.2003.05.007
PMid:14572876
281. C. M. Winget, E. G. Averkin and T. B. Fryer: Quantitative measurement by telemetry of ovulation and oviposition in the fowl. Am J Physiol 209, 853-858 (1965)
282. R. E. MacMillen and C. H. Trost: Nocturnal hypothermia in the Inca dove, Scardafella inca. Comp Biochem Physiol 23, 243-253 (1967)
doi:10.1016/0010-406X(67)90492-6
PMid:5624354
283. F. Halberg and M. B. Visscher: Some physiologic effects of lighting. In: Tenobergen, J. E. (Ed.). Proceedings of the First International Photobiological Congress. Wageningen: Veenman and Zonen, pp. 396-398
284. R. Refinetti: Ultradian rhythms of body temperature and locomotor activity in wild-type and tau-mutant hamsters. Anim Biol 5, 111-115 (1996)
285. G. E. Pickard, R. Kahn and R. Silver: Splitting of the circadian rhythm of body temperature in the golden hamster. Physiol Behav 32, 763-766 (1984)
doi:10.1016/0031-9384(84)90191-4
286. R. Refinetti and M. Menaker: The circadian rhythm of body temperature of normal and tau-mutant golden hamsters. J Therm Biol 17, 129-133 (1992)
doi:10.1016/0306-4565(92)90011-4
287. R. Refinetti: Metabolic heat production, heat loss and the circadian rhythm of body temperature in the rat. Exp Physiol 88, 423-429 (2003)
doi:10.1113/eph8802521
PMid:12719767
288. C. Eastman and A. Rechtschaffen: Circadian temperature and wake rhythms of rats exposed to prolonged continuous illumination. Physiol Behav 31, 417-427 (1983)
doi:10.1016/0031-9384(83)90061-6
289. R. Refinetti and M. Menaker: Independence of heart rate and circadian period in the golden hamster. Am J Physiol 264, R235-R238 (1993)
290. P. Deprés-Brummer, G. Metzger and F. Lévi: Analyses des rythmes de la température corporelle du rat en libre cours. Pathol Biol 44, 150-156 (1996)
291. M. J. H. Kas and D. M. Edgar: Photic phase response curve in Octodon degus: assessment as a function of activity phase preference. Am J Physiol 278, R1385-R1389 (2000)
292. M. B. O. M. Honnebier, S. L. Jenkins and P. W. Nathanielsz: Circadian timekeeping during pregnancy: endogenous phase relationships between maternal plasma hormones and the maternal body temperature rhythm in pregnant rhesus monkeys. Endocrinology 131, 2051-2058 (1992)
doi:10.1210/en.131.5.2051
PMid:1330486
293. E. L. Robinson and C. A. Fuller: Endogenous thermoregulatory rhythms of squirrel monkeys in thermoneutrality and cold. Am J Physiol 276, R1397-R1407 (1999)
294. M. K. Chandrashekaran, G. Marimuthu and L. Geetha: Correlations between sleep and wake in internally synchronized and desynchronized circadian rhythms in humans under prolonged isolation. J Biol Rhythms 12, 26-33 (1997)
doi:10.1177/074873049701200105
PMid:9104688
295. A. Reinberg, F. Halberg, J. Ghata and M. Siffre: Spectre thermique (rythmes de la température rectale) d'une femme adulte avant, pendant et après son isolement souterrain de trois mois. C R Acad Sci 262, 782-785 (1966)
296. C. A. Czeisler, E. D. Weitzman, M. C. Moore-Ede, J. C. Zimmerman and R. S. Knauer: Human sleep: its duration and organization depend on its circadian phase. Science 210, 1264-1267 (1980)
doi:10.1126/science.7434029
PMid:7434029
297. J. Zulley, R. Wever and J. Aschoff: The dependence of onset and duration of sleep on the circadian rhythm of rectal temperature. Pflügers Arch 391, 314-318 (1981)
298. J. Colin, J. Timbal, C. Boutelier, Y. Houdas and M. Siffre: Rhythm of the rectal temperature during a 6-month free-running experiment. J Appl Physiol 25, 170-176 (1968)
299. R. Lund: Personality factors and desynchronization of circadian rhythms. Psychosom Med 36, 224-228 (1974)
300. S. S. Campbell, D. Dawson and J. Zulley: When the human circadian system is caught napping: evidence for endogenous rhythms close to 24 hours. Sleep 16, 638-640 (1993)
301. M. Menaker: Endogenous rhythms of body temperature in hibernating bats. Nature 184, 1251-1252 (1959)
doi:10.1038/1841251a0
302. M. Menaker: The free running period of the bat clock: seasonal variations at low body temperature. J Cell Comp Physiol 57, 81-86 (1961)
doi:10.1002/jcp.1030570204
PMid:13769330
303. B. Jilge, B. Kuhnt, W. Landerer and S. Rest: Circadian temperature rhythms in rabbit pups and in their does. Lab Anim 35, 364-373 (2001)
doi:10.1258/0023677011911831
PMid:11669321
304. S. Daan and J. Aschoff: The entrainment of circadian rhythm. In: Takahashi, J. S., Turek, F. W. & Moore, R. Y. (Eds.). Circadian Clocks (Handbook of Behavioral Neurobiology Volume 12). New York: Kluwer/Plenum, pp. 7-43
305. N. Mrosovsky: Masking: history, definitions, and measurement. Chrobiol Int 16, 415-429 (1999)
doi:10.3109/07420529908998717
PMid:10442236
306. C. H. Johnson, J. A. Elliott and R. Foster: Entrainment of circadian programs. Chrobiol Int 20, 741-774 (2003)
doi:10.1081/CBI-120024211
PMid:14535352
307. L. Rensing and P. Ruoff: Temperature effect on entrainment, phase shifting, and amplitude of circadian clocks and its molecular bases. Chrobiol Int 19, 807-864 (2002)
doi:10.1081/CBI-120014569
PMid:12405549
308. P. Ruoff and L. Rensing: Temperature effects on circadian clocks. J Therm Biol 29, 445-456 (2004)
doi:10.1016/j.jtherbio.2004.07.004
309. F. K. Stephan: Food-entrainable oscillators in mammals. In: Takahashi, J. S., Turek, F. W. & Moore, R. Y. (Eds.). Circadian Clocks (Handbook of Behavioral Neurobiology Volume 12). New York: Kluwer/Plenum, pp. 223-246
310. J. Mendoza: Circadian clocks: setting time by food. J Neuroendocrinol 19, 127-137 (2007)
doi:10.1111/j.1365-2826.2006.01510.x
PMid:17214875
311. B. M. Sweeney and J. W. Hastings: Effects of temperature upon diurnal rhythms. Cold Spring Harb Symp Quant Biol 25, 87-103 (1960)
312. R. Refinetti: The effects of ambient temperature on the body temperature rhythm of rats, hamsters, gerbils, and tree shrews. J Therm Biol 22, 281-284 (1997)
doi:10.1016/S0306-4565(97)00023-5
313. A. E. McKechnie and B. G. Lovegrove: Heterothermic responses in the speckled mousebird (Colius striatus). J Comp Physiol B 171, 507-518 (2001)
doi:10.1007/s003600100201
314. C. T. Downs and M. Brown: Nocturnal heterothermy and torpor in the Malachite sunbird (Nectarinia famosa). Auk 119, 251-260 (2002)
doi:10.1642/0004-8038(2002)119(0251:NHATIT)2.0.CO;2
315. G. Körtner, R. M. Brigham and F. Geiser: Winter torpor in a large bird. Nature 407, 318 (2000)
316. L. C. H. Wang and T. F. Lee: Torpor and hibernation in mammals: metabolic, physiological, and biochemical adaptations. In: Fregly, M. J. & Blatteis, C. M. (Eds.). Handbook of Physiology, Section 4: Environmental Physiology. New York: Oxford University Press, vol. 1, pp. 507-532
317. N. F. Ruby: Hibernation: when good clocks go cold. J Biol Rhythms 18, 275-286 (2003)
doi:10.1177/0748730403254971
PMid:12932080
318. X. Song, G. Körtner and F. Geiser: Temperature selection and use of torpor by the marsupial Sminthopsis macroura. Physiol Behav 64, 675-682 (1998)
doi:10.1016/S0031-9384(98)00136-X
319. M. S. Mojciechowski and M. Jefimow: Is torpor only an advantage? Effect of thermal environment on torpor use in the Siberian hamster (Phodopus sungorus). J Physiol Pharmacol 57, 83-92 (2006)
320. R. Abrams and H. T. Hammel: Hypothalamic temperature in unanesthetized albino rats during feeding and sleeping. Am J Physiol 206, 641-646 (1964)
321. D. L. Ingram and K. F. Legge: Variations in deep body temperature in the young unrestrained pig over the 24 hour period. J Physiol Lond 210, 989-998 (1970)
322. H. Miyazaki, M. Yoshida, K. Samura, H. Matsumoto, F. Ikemoto and M. Tagawa: Ranges of diurnal variation and the pattern of body temperature, blood pressure and heart rate in laboratory Beagle dogs. Exp Anim 51, 95-98 (2002)
doi:10.1538/expanim.51.95
PMid:11871159
323. S. Armstrong: A chronometric approach to the study of feeding behavior. Neurosci Biobehav Rev 4, 27-53 (1980)
doi:10.1016/0149-7634(80)90024-X
324. J. H. Strubbe and S. C. Woods: The timing of meals. Psychol Rev 111, 128-141 (2004)
doi:10.1037/0033-295X.111.1.128
PMid:14756590
325. T. H. Monk, D. J. Buysse, C. F. Reynolds, D. J. Kupfer and P. R. Houck: Subjective alertness rhythms in elderly people. J Biol Rhythms 11, 268-276 (1996)
doi:10.1177/074873049601100308
PMid:8872598
326. J. Carrier and T. H. Monk: Estimating the endogenous circadian temperature rhythm without keeping people awake. J Biol Rhythms 12, 266-277 (1997)
doi:10.1177/074873049701200308
PMid:9181438
327. R. C. Bolles and P. M. Duncan: Daily course of activity and subcutaneous body temperature in hungry and thirsty rats. Physiol Behav 4, 87-89 (1969)
doi:10.1016/0031-9384(69)90018-3
328. E. Hohtola, R. Hissa, A. Pyörnilä, H. Rintamäki and S. Saarela: Nocturnal hypothermia in fasting Japanese quail: the effect of ambient temperature. Physiol Behav 49, 563-567 (1991)
doi:10.1016/0031-9384(91)90281-R
329. S. Sakurada, O. Shido, N. Sugimoto, Y. Hiratsuka, T. Yoda and K. Kanosue: Autonomic and behavioural thermoregulation in starved rats. J Physiol Lond 526, 417-424 (2000)
doi:10.1111/j.1469-7793.2000.00417.x
PMid:10896730 PMCid:2270012
330. M. M. Hotz, M. S. Connolly and C. B. Lynch: Adaptation to daily meal-timing and its effect on circadian temperature rhythms in two inbred strains of mice. Behav Genet 17, 37-51 (1987)
doi:10.1007/BF01066009
PMid:3593153
331. E. Challet, P. Pévet, B. Vivien-Roels and A. Malan: Phase-advanced daily rhythms of melatonin, body temperature, and locomotor activity in food-restricted rats fed during daytime. J Biol Rhythms 12, 65-79 (1997)
doi:10.1177/074873049701200108
PMid:9104691
332. A. Boulamery-Velly, N. Simon, J. Vidal, J. Mouchet and B. Bruguerolle: Effects of three-hour restricted food access during the light period on circadian rhythms of temperature, locomotor activity, and heart rate in rats. Chrobiol Int 22, 489-498 (2005)
doi:10.1081/CBI-200062366
PMid:16076649
333. P. M. Fuller, J. Lu and C. B. Saper: Differential rescue of light- and food-entrainable circadian rhythms. Science 320, 1074-1077 (2008)
doi:10.1126/science.1153277
PMid:18497298
334. K. Horst, L. B. Mendel and F. G. Benedict: The metabolism of the albino rat during prolonged fasting at two different environmental temperatures. J Nutr 3, 177-200 (1930)
335. B. A. Campbell and G. S. Lynch: Influence of hunger and thirst on the relationship between spontaneous activity and body temperature. J Comp Physiol Psychol 65, 492-498 (1968)
doi:10.1037/h0025823
PMid:5667390
336. C. Duchamp, H. Barré, D. Delage, J. L. Rouanet, F. Cohen-Adad and Y. Minaire: Nonshivering thermogenesis and adaptation to fasting in king penguin chicks. Am J Physiol 257, R744-R751 (1989)
337. M. S. Klein, C. A. Conn and M. J. Kluger: Behavioral thermoregulation in mice inoculated with influenza virus. Physiol Behav 52, 1133-1139 (1992)
doi:10.1016/0031-9384(92)90472-E
338. M. E. Rashotte, P. S. Basco and R. P. Henderson: Daily cycles in body temperature, metabolic rate, and substrate utilization in pigeons: influence of amount and timing of food consumption. Physiol Behav 57, 731-746 (1995)
doi:10.1016/0031-9384(94)00315-7
339. F. D. Vogt and G. R. Lynch: Influence of ambient temperature, nest availability, huddling, and daily torpor on energy expenditure in the white-footed mouse Peromyscus leucopus. Physiol Zool 55, 56-63 (1982)
340. M. G. Tannenbaum and E. B. Pivorun: Differential effect of food restriction on the induction of daily torpor in Peromyscus maniculatus and P. leucopus. J Therm Biol 12, 159-162 (1987)
doi:10.1016/0306-4565(87)90057-X
341. G. Heldmaier, S. Steinlechner, T. Ruf, H. Wiesinger and M. Klingenpor: Photoperiod and thermoregulation in vertebrates: body temperature rhythms and thermogenic acclimation. J Biol Rhythms 4, 251-265 (1989)
doi:10.1177/074873048900400211
342. N. F. Ruby, N. Ibuka, B. M. Barnes and I. Zucker: Suprachiasmatic nuclei influence torpor and circadian temperature rhythms in hamsters. Am J Physiol 257, R210-R215 (1989)
343. G. T. H. Ellison and J. D. Skinner: The influence of ambient temperature on spontaneous daily torpor in pouched mice (Saccostomus campestris: Rodentia: Cricetidae) from southern Africa. J Therm Biol 17, 25-31 (1992)
doi:10.1016/0306-4565(92)90016-9
344. R. Prinzinger, T. Schäfer and K. L. Schuchmann: Energy metabolism, respiratory quotient and breathing parameters in two convergent small bird species: the fork-tailed sunbird and the Chilean hummingbird. J Therm Biol 17, 71-79 (1992)
doi:10.1016/0306-4565(92)90001-V
345. F. Geiser and P. Masters: Torpor in relation to reproduction in the mulgara, Dasycercus cristicauda (Dasyuridae: Marsupialia). J Therm Biol 19, 33-40 (1994)
doi:10.1016/0306-4565(94)90007-8
346. J. C. Holloway and F. Geiser: Reproductive status and torpor of the marsupial Sminthopsis crassicaudata: effect of photoperiod. J Therm Biol 21, 373-380 (1996)
doi:10.1016/S0306-4565(96)00023-X
347. S. Ortmann and G. Heldmaier: Spontaneous daily torpor in Malagasy mouse lemurs. Naturwissenschaften 84, 28-32 (1997)
doi:10.1007/s001140050344
PMid:9050004
348. C. Turbill, B. S. Law and F. Geiser: Summer torpor in a free-ranging bat from subtropical Australia. J Therm Biol 28, 223-226 (2003)
doi:10.1016/S0306-4565(02)00067-0
349. C. Turbill, G. Körtner and F. Geiser: Natural use of heterothermy by a small, tree-roosting bat during summer. Physiol Biochem Zool 76, 868-876 (2003)
doi:10.1086/378915
PMid:14988802
350. N. H. Phillips and R. J. Berger: Regulation of body temperature, metabolic rate, and sleep in fasting pigeons diurnally infused with glucose or saline. J Comp Physiol B 161, 311-318 (1991)
doi:10.1007/BF00262313
351. J. Ostheim: Coping with food-limited conditions: feeding behavior, temperature preference, and nocturnal hypothermia in pigeons. Physiol Behav 51, 353-361 (1992)
doi:10.1016/0031-9384(92)90153-S
352. R. Prinzinger, E. Schleucher and A. Preßmar: Langzeittelemetrie der Körpertemperatur mit synchroner Bestimmung des Energiestoffwechsels beim Blaunackenmausvogel (Urocolius macrourus) unter Normal- und Lethargiebedingungen (Torpor). J Ornithol 133, 446-450 (1992)
doi:10.1007/BF01640473
353. A. E. McKechnie and B. G. Lovegrove: Facultative hypothermic responses in an Afrotropical arid-zone passerine, the red-headed finch (Amadina erythrocephala). J Comp Physiol B 173, 339-346 (2003)
doi:10.1007/s00360-003-0341-0
354. J. W. Hudson: Temperature regulation and torpidity in the pigmy mouse, Baiomys taylori. Physiol Zool 38, 243-254 (1965)
355. J. R. Nestler: Relationships between respiratory quotient and metabolic rate during entry to and arousal from daily torpor in deer mice (Peromyscus maniculatus). Physiol Zool 63, 504-515 (1990)
356. F. Damiola, N. Le Minh, N. Preitner, B. Kornmann, F. Fleury-Olela and U. Schibler: Restricted feeding uncouples circadian oscillators in peripheral tissues from the central pacemaker in the suprachiasmatic nucleus. Genes Dev 14, 2950-2961 (2000)
doi:10.1101/gad.183500
357. S. Liu, X. M. Chen, T. Nagashima Yoda, Fukuda K., Y. and K. Kanosue: Involvement of the suprachiasmatic nucleus in body temperature modulation by food deprivation in rats. Brain Res 929, 26-36 (2002)
doi:10.1016/S0006-8993(01)03374-1
PMid:11852028
358. N. Pecoraro, F. Gomez, K. Laugero and M. F. Dallman: Brief access to sucrose engages food-entrainable rhythms in food-deprived rats. Behav Neurosci 116, 757-776 (2002)
doi:10.1037/0735-7044.116.5.757
PMid:12369798
359. D. P. King and J. S. Takahashi: Molecular genetics of circadian rhythms in mammals. Ann Rev Neurosci 23, 713-742 (2000)
doi:10.1146/annurev.neuro.23.1.713
PMid:10845079
360. S. M. Reppert and D. R. Weaver: Molecular analysis of mammalian circadian rhythms. Ann Rev Physiol 63, 647-676 (2001)
doi:10.1146/annurev.physiol.63.1.647
PMid:11181971
361. A. Heusner: Variation nycthémérale de la température centrale chez le rat adapté à la neutralité thermique. C R Séances Soc Biol Strasb 153, 1258-1261 (1959)
362. I. Tang, D. M. Murakami and C. A. Fuller: Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms. Am J Physiol 276, R1195-R1202 (1999)
363. R. Refinetti: Relationship between the daily rhythms of locomotor activity and body temperature in eight mammalian species. Am J Physiol 277, R1493-R1500 (1999)
364. B. Saltin, A. P. Gagge and J. A. J. Stolwijk: Body temperature and sweat during thermal transients caused by exercise. J Appl Physiol 28, 318-327 (1970)
365. M. Cabanac, D. J. Cunningham and J. A. J. Stolwijk: Thermoregulatory set point during exercise: a behavioral approach. J Comp Physiol Psychol 76, 94-102 (1971)
doi:10.1037/h0031050
PMid:5571306
366. P. Webb: Daily activity and body temperature. Eur J Appl Physiol 66, 174-177 (1993)
doi:10.1007/BF01427059
367. M. R. Deschenes, W. J. Kraemer, J. A. Bush, T. A. Doughty, D. Kim, K. M. Mullen and K. Ramsey: Biorhythmic influences on functional capacity of human muscle and physiological responses. Med Sci Sports Exerc 30, 1399-1407 (1998)
doi:10.1097/00005768-199809000-00008
368. J. Arnold, J. LeBlanc, J. Cote, J. Lalonde and D. Richard: Exercise suppression of thermoregulatory thermogenesis in warm- and cold-acclimated rats. Can J Physiol Pharmacol 64, 922-926 (1986)
369. M. K. Yousef, W. D. Robertson, D. B. Dill and H. D. Johnson: Energetic cost of running in the antelope ground squirrel Ammospermophilus leucurus. Physiol Zool 46, 139-147 (1973)
370. E. Zerba and G. E. Walsberg: Exercise-generated heat contributes to thermoregulation by Gambel's quail in the cold. J Exp Biol 171, 409-422 (1992)
371. P. Golja, O. Eiken, S. Rodman, B. Sirok and I. B. Mekjavic: Core temperature circadian rhythm during 35 days of horizontal bed rest. Proc Eur Symp Life Sci Res Space 8, 161-162 (2002)
372. R. C. Bolles, P. M. Duncan, N. E. Grossen and C. F. Matter: Relationship between activity level and body temperature in the rat. Psychol Rep 23, 991-994 (1968)
373. C. J. Gordon and Y. Yang: Contribution of spontaneous motor activity to the 24 hour control of body temperature in male and female rats. J Therm Biol 22, 59-68 (1997)
doi:10.1016/S0306-4565(96)00035-6
374. S. Folkard, D. S. Minors and J. M. Waterhouse: "Demasking" the temperature rhythm after simulated time zone transitions. J Biol Rhythms 6, 81-91 (1991)
doi:10.1177/074873049100600109
PMid:1773083
375. E. B. Klerman, H. B. Gershengorn, J. F. Duffy and R. E. Kronauer: Comparisons of the variability of three markers of the human circadian pacemaker. J Biol Rhythms 17, 181-193 (2002)
doi:10.1177/074873002129002474
PMid:12002165
376. I. Schmidt, A. Barone and H. J. Carlisle: Diurnal cycle of core temperature in huddling, week-old rat pups. Physiol Behav 37, 105-109 (1986)
doi:10.1016/0031-9384(86)90391-4
377. D. E. Spiers: Nocturnal shifts in thermal and metabolic responses of the immature rat. J Appl Physiol 64, 2119-2124 (1988)
378. B. Nuesslein and I. Schmidt: Development of circadian cycle of core temperature in juvenile rats. Am J Physiol 259, R270-R276 (1990)
379. B. Nuesslein-Hildesheim, K. Imai-Matsumura, H. Döring and I. Schmidt: Pronounced juvenile circadian core temperature rhythms exist in several strains of rats but not in rabbits. J Comp Physiol B 165, 13-17 (1995)
doi:10.1007/BF00264681
380. K. Imai-Matsumura, R. Kaul and I. Schmidt: Juvenile circadian core temperature rhythm in Wistar and Lean (Fa/-) Zucker rat pups. Physiol Behav 57, 135-139 (1995)
doi:10.1016/0031-9384(94)00217-S
381. E. L. Seifert and J. P. Mortola: Light-dark differences in the effects of ambient temperature on gaseous metabolism in newborn rats. J Appl Physiol 88, 1853-1858 (2000)
382. E. M. W. Kittrell and E. Satinoff: Development of the circadian rhythm of body temperature in rats. Physiol Behav 38, 99-104 (1986)
doi:10.1016/0031-9384(86)90138-1
383. B. Nuesslein-Hildesheim and I. Schmidt: Is the circadian core temperature rhythm of juvenile rats due to a periodic blockade of thermoregulatory thermogenesis? Pflügers Arch 427, 450-454 (1994)
doi:10.1007/BF00374260
PMid:7971143
384. B. Jilge, B. Kuhnt, W. Landerer and S. Rest: Circadian thermoregulation in suckling rabbit pups. J Biol Rhythms 15, 329-335 (2000)
doi:10.1177/074873000129001431
PMid:10942264
385. A. S. Macaulay, G. L. Hahn, D. H. Clark and D. V. Sisson: Comparison of calf housing types and tympanic temperature rhythms in Holstein calves. J Dairy Sci 78, 856-862 (1995)
386. G. Caola Piccione, G. and R. Refinetti: Maturation of the daily body temperature rhythm in sheep and horse. J Therm Biol 27, 333-336 (2002)
doi:10.1016/S0306-4565(01)00076-6
387. G. Piccione, F. Fazio, E. Giudice and R. Refinetti: Body size and the daily rhythm of body temperature in dogs. J Therm Biol 34, 171-175 (2009)
doi:10.1016/j.jtherbio.2009.01.004
388. G. Piccione and R. Refinetti: Thermal chronobiology of domestic animals. Front Biosci 8, 258-264 (2003)
doi:10.2741/1040
PMid:12700024
389. N. Kleitman, S. Titelbaum and H. Hoffmann: The establishment of the diurnal temperature cycle. Am J Physiol 119, 48-54 (1937)
390. K. Abe and S. Fukui: The individual development of circadian temperature rhythm in infants. J Interdiscipl Cycle Res 10, 227-232 (1979)
391. J. J. Aarseth, T. J. Van't Hof and K. A. Stokkan: Melatonin is rhythmic in newborn seals exposed to continuous light. J Comp Physiol B 173, 37-42 (2003)
392. L. Tamarkin, S. M. Reppert, D. J. Orloff, D. C. Klein, S. M. Yellon and B. D. Goldman: Ontogeny of the pineal melatonin rhythm in the Syrian (Mesocricetus auratus) and Siberian (Phodopus sungorus) hamsters and in the rat. Endocrinology 107, 1061-1064 (1980)
doi:10.1210/endo-107-4-1061
PMid:7408759
393. A. Attanasio, K. Rager and D. Gupta: Ontogeny of circadian rhythmicity for melatonin, serotonin, and N-acetylserotonin in humans. J Pineal Res 3, 251-256 (1986)
doi:10.1111/j.1600-079X.1986.tb00747.x
PMid:3772723
394. J. Ardura, R. Gutierrez, J. Andres and T. Agapito: Emergence and evolution of the circadian rhythm of melatonin in children. Horm Res 59, 66-72 (2003)
doi:10.1159/000068571
PMid:12589109
395. S. M. Reppert and W. J. Schwartz: The suprachiasmatic nuclei of the fetal rat: characterization of a functional circadian clock using (14).C-labeled deoxyglucose. J Neurosci 4, 1677-1682 (1984)
396. S. Shibata and R. Y. Moore: Development of neuronal activity in the rat suprachiasmatic nucleus. Brain Res 431, 311-315 (1987)
397. Z. Bendová, A. Sumová and H. Illnerová: Development of circadian rhythmicity and photoperiodic response in subdivisions of the rat suprachiasmatic nucleus. Dev Brain Res 148, 105-112 (2004)
doi:10.1016/j.devbrainres.2003.10.007
PMid:14757524
398. D. C. Houghton, I. R. Young and I. C. McMillen: Evidence for hypothalamic control of the diurnal rhythms in prolactin and melatonin in the fetal sheep during late gestation. Endocrinology 136, 218-223 (1995)
doi:10.1210/en.136.1.218
PMid:7828534
399. V. H. Parraguez, G. J. Valenzuela, M. Vergara, C. A. Ducsay, S. M. Yellon and M. Serón-Ferré: Effect of constant light on fetal and maternal prolactin rhythms in sheep. Endocrinology 137, 2355-2361 (1996)
doi:10.1210/en.137.6.2355
PMid:8641186
400. K. Brück and P. Hinckel: Ontogenetic and adaptive adjustments in the thermoregulatory system. In: Fregly, M. J. & Blatteis, C. M. (Eds.). Handbook of Physiology, Section 4: Environmental Physiology. New York: Oxford University Press, pp. 597-611
401. M. A. Brock: Biological clocks and aging. Rev Biol Res Aging 2, 445-462 (1985)
402. A. Adan: Diferencias individuales en las variaciones diurnas fisiologicas y comportamentales. Rev Latinoam Psicol 29, 81-114 (1997)
403. F. W. Turek, K. Scarbrough, P. Penev, S. Labyak, V. S. Valentinuzzi and O. Van Reeth: Aging of the mammalian circadian system. In: Takahashi, J. S., Turek, F. W. & Moore, R. Y. (Eds.). Circadian Clocks (Handbook of Behavioral Neurobiology Volume 12). New York: Kluwer/Plenum, pp. 291-317
404. M. V. Vitiello, R. G. Smallwood, D. H. Avery, R. A. Pascualy, D. C. Martin and P. N. Prinz: Circadian temperature rhythms in young adult and aged men. Neurobiol Aging 7, 97-100 (1986)
doi:10.1016/0197-4580(86)90146-6
PMid:3960269
405. Y. Touitou, A. Reinberg, A. Bogdan, A. Auzéby, H. Beck and C. Touitou: Age-related changes in both circadian and seasonal rhythms of rectal temperature with special reference to senile dementia of Alzheimer type. Gerontology 32, 110-118 (1986)
doi:10.1159/000212774
PMid:3710170
406. E. J. Yunis, G. Fernandes, W. Nelson and F. Halberg: Circadian temperature rhythms and aging in rodents. In: Scheving, L. E., Halberg, F. & Pauly, J. E. (Eds.). Chronobiology. Tokyo: Igaku Shoin, pp. 358-363
407. J. Halberg, E. Halberg, P. Regal and F. Halberg: Changes with age characterize circadian rhythm in telemetered core temperature of stroke-prone rats. J Gerontol 36, 28-30 (1981)
408. G. C. Koster-van-Hoffen, M. Mirmiran, N. P. A. Bos, W. Witting, P. Delagrande and B. Guardiola-Lemaitre: Effects of a novel melatonin analog on circadian rhythms of body temperature and activity in young, middle-aged, and old rats. Neurobiol Aging 14, 565-569 (1993)
doi:10.1016/0197-4580(93)90040-I
PMid:8295659
409. R. B. McDonald, T. M. Hoban-Higgins, R. C. Ruhe, C. A. Fuller and B. A. Horwitz: Alterations in endogenous circadian rhythm of core temperature in senescent Fischer 344 rats. Am J Physiol 276, R824-R830 (1999)
410. R. Frank and C. Tankersley: Air pollution and daily mortality: a hypothesis concerning the role of impaired homeostasis. Environ Health Perspect 110, 61-65 (2002)
411. C. P. May, L. Hasher and E. R. Stoltzfus: Optimal time of day and the magnitude of age differences in memory. Psychol Sci 4, 326-330 (1993)
doi:10.1111/j.1467-9280.1993.tb00573.x
412. E. K. Baehr, W. Revelle and C. I. Eastman: Individual differences in the phase and amplitude of the human circadian temperature rhythm with an emphasis on morningness-eveningness. J Sleep Res 9, 117-127 (2000)
doi:10.1046/j.1365-2869.2000.00196.x
PMid:10849238
413. E. B. Klerman, J. F. Duffy, D. J. Dijk and C. A. Czeisler: Circadian phase resetting in older people by ocular bright light exposure. J Investig Med 49, 30-40 (2001)
doi:10.2310/6650.2001.34088
414. D. L. Robilliard, S. N. Archer, J. Arendt, S. W. Lockley, L. M. Hack, J. English, D. Leger, M. G. Smits, A. Williams, D. J. Skene and M. von Schantz: The 3111 Clock gene polymorphism is not associated with sleep and circadian rhythmicity in phenotypically characterized human subjects. J Sleep Res 11, 305-312 (2002)
doi:10.1046/j.1365-2869.2002.00320.x
PMid:12464098
415. C. S. Pittendrigh and S. Daan: Circadian oscillations in rodents: a systematic increase of their frequency with age. Science 186, 548-550 (1974)
doi:10.1126/science.186.4163.548
PMid:4469680
416. L. P. Morin: Age-related changes in hamster circadian period, entrainment, and rhythm splitting. J Biol Rhythms 3, 237-248 (1988)
doi:10.1177/074873048800300302
417. R. S. Rosenberg, P. C. Zee and F. W. Turek: Phase response curves to light in young and old hamsters. Am J Physiol 261, R491-R495 (1991)
418. L. P. Morin: Age, but not pineal status, modulates circadian periodicity of golden hamsters. J Biol Rhythms 8, 189-197 (1993)
doi:10.1177/074873049300800302
PMid:8280908
419. N. Viswanathan and F. C. Davis: Suprachiasmatic nucleus grafts restore circadian function in aged hamsters. Brain Res 686, 10-16 (1995)
doi:10.1016/0006-8993(95)00423-N
PMid:7583260
420. M. Oklejewicz, R. A. Hut, S. Daan, A. S. I. Loudon and A. J. Stirland: Metabolic rate changes proportionally to circadian frequency in tau mutant Syrian hamster. J Biol Rhythms 12, 413-422 (1997)
421. D. E. Kolker, H. Fukuyama, D. S. Huang, J. S. Takahashi, T. H. Horton and F. W. Turek: Aging alters circadian and light-induced expression of clock genes in golden hamsters. J Biol Rhythms 18, 159-169 (2003)
doi:10.1177/0748730403251802
PMid:12693870
422. W. Witting, M. Mirmiran, N. P. A. Bos and D. F. Swaab: The effect of old age on the free-running period of circadian rhythms in rat. Chrobiol Int 11, 103-112 (1994)
doi:10.3109/07420529409055896
PMid:8033238
423. F. C. Davis and M. Menaker: Development of the mouse circadian pacemaker: independence from environmental cycles. J Comp Physiol A 143, 527-539 (1981)
doi:10.1007/BF00609919
424. B. Possidente, S. McEldowney and A. Pabon: Aging lengthens circadian period for wheel-running activity in C57BL mice. Physiol Behav 57, 575-579 (1995)
doi:10.1016/0031-9384(94)00298-J
425. H. Pohl: Does aging affect the period of the circadian pacemaker in vertebrates? Naturwissenschaften 80, 478-481 (1993)
doi:10.1007/BF01136044
PMid:8264804
426. C. A. Czeisler, J. F Duffy, T. L. Shanahan, E. N. Brown, J. F. Mitchell, D. W. Rimmer, J. M. Ronda, E. J. Silva, J. S. Allan, J. S. Emens, D. J. Dijk and R. E. Kronauer: Stability, precision, and near-24-hour period of the human circadian pacemaker. Science 284, 2177-2181 (1999)
doi:10.1126/science.284.5423.2177
PMid:10381883
427. J. Aschoff: The circadian rhythm of body temperature as a function of body size. In: Taylor, C. R., Johansen, K. & Bolis, L. (Eds.). A Companion to Animal Physiology. Cambridge, UK: Cambridge University Press, pp. 173-188
428. J. P. Mortola and C. Lanthier: Scaling the amplitudes of the circadian pattern of resting oxygen consumption, body temperature and heart rate in mammals. Comp Biochem Physiol A 139, 83-95 (2004)
doi:10.1016/j.cbpb.2004.07.007
429. P. R. Morrison and F. A. Ryser: Weight and body temperature in mammals. Science 116, 231-232 (1952)
doi:10.1126/science.116.3009.231
PMid:17770935
430. B. G. Lovegrove: The influence of climate on the basal metabolic rate of small mammals: a slow-fast metabolic continuum. J Comp Physiol B 173, 87-112 (2003)
431. C. R. White and R. S. Seymour: Mammalian basal metabolic rate is proportional to body mass 2/3. Proc Nat Acad Sci USA 100, 4046-4049 (2003)
doi:10.1073/pnas.0436428100
432. K. Adam: Human body temperature is inversely correlated with body mass. Eur J Appl Physiol 58, 471-475 (1989)
doi:10.1007/BF02330699
433. A. Clarke and P. Rothery: Scaling of body temperature in mammals and birds. Funct Ecol 22, 58-67 (2008)
434. M. H. Johnson and B. J. Everitt: Essential Reproduction, 5th Edition. Oxford, U.K.: Blackwell
435. R. Sridaran and C. E. McCormack: Parallel effects of light signals on the circadian rhythms of running activity and ovulation in rats. J Endocrinol 85, 111-120 (1980)
doi:10.1677/joe.0.0850111
PMid:7190182
436. E. Palmer, M. A. Driancourt and R. Ortavant: Photoperiodic stimulation of the mare during winter anoestrus. J Reprod Fertil 32(S), 275-282 (1982)
437. G. S. Lewis and S. K. Newman: Changes throughout estrous cycles of variables that might indicate estrus in dairy cows. J Dairy Sci 67, 146-152 (1984)
438. R. Rajamahendran, J. Robinson, S. Desbottes and J. S. Walton: Temporal relationships among estrus, body temperature, milk yield, progesterone and luteinizing hormone levels, and ovulation in dairy cows. Theriogenology 31, 1173-1182 (1989)
doi:10.1016/0093-691X(89)90086-1
PMid:16726635
439. L. A. Walker, L. Cornell, K. D. Dahl, N. M. Czekala, C. M. Dargen, B. Joseph, A. J. W. Hsueh and B. L. Lasley: Urinary concentrations of ovarian steroid hormone metabolites and bioactive follicle-stimulating hormone in killer whales (Orcinus orchus) during ovarian cycles and pregnancy. Biol Reprod 39, 1013-1020 (1988)
doi:10.1095/biolreprod39.5.1013
PMid:3146355
440. L. Häster and H. G. Erkert: Alteration of circadian period length does not influence the ovarian cycle length in common marmosets, Callithrix j. jacchus (Primates). Chrobiol Int 10, 165-175 (1993)
doi:10.3109/07420529309073885
PMid:8319317
441. S. E. Shideler, A. Savage, A. M. Ortuño, E. A. Moorman and B. L. Lasley: Monitoring female reproductive function by measurement of fecal estrogen and progesterone metabolites in the white-faced saki (Pithecia pithecia). Am J Primatol 32, 95-108 (1994)
doi:10.1002/ajp.1350320203
442. C. S. Asa, F. Fischer, E. Carrasco and C. Puricelli: Correlation between urinary pregnanediol glucuronide and basal body temperature in female orangutans, Pongo pygmaeus. Am J Primatol 34, 275-281 (1994)
doi:10.1002/ajp.1350340304
443. N. Nagamine, Y. Nambo, S. Nagata, K. Nagaoka, N. Tsunoda, H. Taniyama, Y. Tanaka, A. Tohei, G. Watanabe and K. Taya: Inhibin secretion in the mare: localization of inhibin alpha, beta-A, and beta-B subunits in the ovary. Biol Reprod 59, 1392-1398 (1998)
doi:10.1095/biolreprod59.6.1392
PMid:9828183
444. H. S. Kooistra, A. C. Okkens, M. M. Bevers, C. Popp-Snijders, B. van Haaften, S. J. Dieleman and J. Schoemaker: Concurrent pulsatile secretion of luteinizing hormone and follicle-stimulating hormone during different phases of the estrous cycle and anestrus in Beagle bitches. Biol Reprod 60, 65-71 (1999)
doi:10.1095/biolreprod60.1.65
PMid:9858487
445. H. J. McMillan and K. E. Wynne-Edwards: Divergent reproductive endocrinology of the estrous cycle and pregnancy in dwarf hamsters (Phodopus). Comp Biochem Physiol A 124, 53-67 (1999)
doi:10.1016/S1095-6433(99)00090-2
446. C. A. Gray, F. F. Bartol, K. M. Taylor, A. A. Wiley, W. S. Ramsey, T. L. Ott, F. W. Bazer and T. E. Spencer: Ovine uterine gland knock-out model: effects of gland ablation on the estrous cycle. Biol Reprod 62, 448-456 (2000)
doi:10.1095/biolreprod62.2.448
PMid:10642586
447. D. C. Skinner, T. A. Richter, B. Malpaux and J. D. Skinner: Annual ovulation cycles in an aseasonal breeder, the springbok (Antidorcas marsupialis). Biol Reprod 64, 1176-1182 (2001)
doi:10.1095/biolreprod64.4.1176
PMid:11259265
448. R. Duggavathi, P. M. Bartlewski, D. M. W. Barrett and N. C. Rawlings: Use of high-resolution transrectal ultrasonography to assess changes in numbers of small ovarian antral follicles and their relationships to the emergence of follicular waves in cyclic ewes. Theriogenology 60, 495-510 (2003)
doi:10.1016/S0093-691X(03)00041-4
PMid:12763163
449. M. West, D. Galloway, J. Shaw, A. Trouson and M. C. J. Paris: Oestrous cycle of the common wombat, Vombatus ursinus, in Victoria, Australia. Reprod Fertil Dev 16, 339-346 (2004)
doi:10.1071/RD03058
450. J. L. Brown, S. L. Walker and T. Moeller: Comparative endocrinology of cycling and non-cycling Asian (Elephas maximus) and African (Loxodonta africana) elephants. Gen Comp Endocrinol 136, 360-370 (2004)
doi:10.1016/j.ygcen.2004.01.013
PMid:15081836
451. S. Atsalis, S. W. Margulis, A. Bellem and N. Wielebnowski: Sexual behavior and hormonal estrus cycles in captive aged lowland gorillas (Gorilla gorilla). Am J Primatol 62, 123-132 (2004)
doi:10.1002/ajp.20010
PMid:14983470
452. J. R. Brobeck, M. Wheatland and J. L. Strominger: Variations in regulation of energy exchange associated with estrus, diestrus and pseudopregnancy in rats. Endocrinology 40, 65-72 (1947)
doi:10.1210/endo-40-2-65
453. G. Bouchard, R. S. Youngquist, D. Vaillancourt, G. F. Krause, P. Guay and M. Paradis: Seasonality and variability of the interestrous interval in the bitch. Theriogenology 36, 41-50 (1991)
doi:10.1016/0093-691X(91)90432-D
PMid:16726976
454. N. J. Beijerink, S. J. Dieleman, H. S. Kooistra and A. C. Okkens: Low doses of bromocriptine shorten the interestrous interval in the bitch without lowering plasma prolactin concentration. Theriogenology 60, 1379-1386 (2003)
doi:10.1016/S0093-691X(03)00170-5
PMid:14511790
455. D. F. Hardy: The effect of constant light on the estrous cycle and behavior of the female rat. Physiol Behav 5, 421-425 (1970)
doi:10.1016/0031-9384(70)90246-5
456. G. A. Johnson, M. D. Stewart, C. A. Gray, Y. Choi, R. C. Burghardt, L. Y. Yu-Lee, F. W. Bazer and T. E. Spencer: Effects of the estrous cycle, pregnancy, and interferon tau on 2',5'-oligoadenylate synthetase expression in the ovine uterus. Biol Reprod 64, 1392-1399 (2001)
doi:10.1095/biolreprod64.5.1392
PMid:11319143
457. J. L. Zehr, P. L. Tannenbaum, B. Jones and K. Wallen: Peak occurrence of female sexual initiation predicts day of conception in rhesus monkeys (Macaca mulatta). Reprod Fertil Dev 12, 397-404 (2000)
doi:10.1071/RD00080
458. J. Handler, A. Wüstenhagen, D. Schams, H. Kindahl and C. Aurich: Estrous cycle characteristics, luteal function, secrection of oxytocin and plasma concentrations of 5-keto-13,14- dihydro-PGF2alpha after administration of low doses of prostaglandin F2alpha in pony mares. Theriogenology 61, 1573-1582 (2004)
doi:10.1016/j.theriogenology.2003.09.005
PMid:15036986
459. F. Wollnik and F. W. Turek: Estrous correlated modulations of circadian and ultradian wheel-running activity rhythms in LEW/Ztm rats. Physiol Behav 43, 389-396 (1988)
doi:10.1016/0031-9384(88)90204-1
460. A. J. P. Francis and G. J. Coleman: The effect of ambient temperature cycles upon circadian running and drinking activity in male and female laboratory rats. Physiol Behav 43, 471-477 (1988)
doi:10.1016/0031-9384(88)90121-7
461. S. Kent, M. Hurd and E. Satinoff: Interactions between body temperature and wheel running over the estrous cycle in rats. Physiol Behav 49, 1079-1084 (1991)
doi:10.1016/0031-9384(91)90334-K
462. K. D. Redden, A. D. Kennedy, J. R. Ingalls and T. L. Gilson: Detection of estrus by radiotelemetric monitoring of vaginal and ear skin temperature and pedometer measurements of activity. J Dairy Sci 76, 713-721 (1993)
463. B. Rauth-Widmann, E. Fuchs and H. G. Erkert: Infradian alteration of circadian rhythms in owl monkeys (Aotus lemurinus griseimembra): an effect of estrous? Physiol Behav 59, 11-18 (1996)
doi:10.1016/0031-9384(95)02009-8
464. R. Refinetti and M. Menaker: Evidence for separate control of estrous and circadian periodicity in the golden hamster. Behav Neur Biol 58, 27-36 (1992)
doi:10.1016/0163-1047(92)90862-X
PMid:1417668
465. B. L. Marrone, R. T. Gentry and G. N. Wade: Gonadal hormones and body temperature in rats: effects of estrous cycles, castration and steroid replacement. Physiol Behav 17, 419-425 (1976)
doi:10.1016/0031-9384(76)90101-3
466. R. W. Krohmer and D. Crews: Temperature activation of courtship behavior in the male red-sided garter snake (Thamnophis sirtalis parietalis): role of the anterior hypothalamus-preoptic area. Behav Neurosci 101, 228-236 (1987)
doi:10.1037/0735-7044.101.2.228
PMid:3580125
467. J. A. Czaja and P. C. Butera: Body temperature and temperature gradients: changes during the estrous cycle and in response to ovarian steroids. Physiol Behav 36, 591-596 (1986)
doi:10.1016/0031-9384(86)90339-2
468. T. R. Wrenn, J. Bitman and J. F. Sykes: Body temperature variations in dairy cattle during the estrous cycle and pregnancy. J Dairy Sci 41, 1071-1076 (1958)
469. D. P. Fordham, P. Rowlinson and T. T. McCarthy: Oestrus detection in dairy cows by milk temperature measurement. Res Vet Sci 44, 366-374 (1988)
470. B. L. Kyle, A. D. Kennedy and J. A. Small: Measurement of vaginal temperature by radiotelemetry for the prediction of estrus in beef cows. Theriogenology 49, 1437-1449 (1998)
doi:10.1016/S0093-691X(98)00090-9
PMid:10732008
471. J. Aschoff: Circadian rhythm of activity and of body temperature. In: Hardy, J. D., Gagge, A. P. & Stolwijk, J. A. J. (Eds.). Physiological and Behavioral Temperature Regulation. Springfield, Ill.: Charles C. Thomas, pp. 905-919
472. H. Hensel: Thermoreception and Temperature Regulation. New York: Academic Press
473. M. J. Kluger: Fever: role of pyrogens and cryogens. Physiol Rev 71, 93-128 (1991)
474. O. Shido: Day-night variation of thermoregulatory responses to intraperitoneal electric heating in rats. J Therm Biol 12, 273-279 (1987)
doi:10.1016/0306-4565(87)90028-3
475. R. Graf: Diurnal changes of thermoregulatory functions in pigeons. II. Spinal thermosensitivity. Pflügers Arch 386, 181-185 (1980)
doi:10.1007/BF00584206
PMid:7191972
476. H. C. Heller, R. Graf and W. Rautenberg: Circadian and arousal state influences on thermoregulation in the pigeon. Am J Physiol 245, R321-R328 (1983)
477. C. B. Wenger, M. F. Roberts, J. A. J. Stolwijk and E. R. Nadel: Nocturnal lowering of thresholds for sweating and vasodilation. J Appl Physiol 41, 15-19 (1976)
478. K. Aoki, N. Kondo, M. Shibasaki, S. Takano, H. Tominaga and T. Katsuura: Circadian variation of sweating responses to passive heat stress. Acta Physiol Scand 161, 397-402 (1997)
doi:10.1046/j.1365-201X.1997.d01-1981.x
PMid:9401593
479. K. Aoki, D. P. Stephens, A. R. Saad and J. M. Johnson: Cutaneous vasoconstrictor response to whole body skin cooling is altered by time of day. J Appl Physiol 94, 930-934 (2003)
480. D. L. Ingram: The efficiency of operant thermoregulatory behaviour in pigs as determined from the rate of oxygen consumption. Pflügers Arch 353, 139-149 (1975)
doi:10.1007/BF00599874
PMid:1167667
481. I. Schmidt: Interactions of behavioral and autonomic thermoregulation in heat stressed pigeons. Pflügers Arch 374, 47-55 (1978)
doi:10.1007/BF00585696
PMid:567332
482. E. R. Adair and B. A. Wright: Behavioral thermoregulation in the squirrel monkey when response effort is varied. J Comp Physiol Psychol 90, 179-184 (1976)
doi:10.1037/h0077197
PMid:814149
483. I. Schmidt and E. Simon: Interaction of behavioral and autonomic thermoregulation in cold exposed pigeons. J Comp Physiol 133, 151-157 (1979)
doi:10.1007/BF00657530
484. C. J. Gordon: Behavioral and autonomic thermoregulation in mice exposed to microwave radiation. J Appl Physiol 55, 1242-1248 (1983)
485. C. J. Gordon, M. D. Long, and K. S. Fehlner: Behavioural and autonomic thermoregulation in hamsters during microwave-induced heat exposure. J Therm Biol 9, 271-277 (1984)
doi:10.1016/0306-4565(84)90008-1
486. R. Refinetti and H. J. Carlisle: Complementary nature of heat production and heat intake during behavioral thermoregulation in the rat. Behav Neur Biol 46, 64-70 (1986)
doi:10.1016/S0163-1047(86)90905-2
PMid:3729897
487. R. Beste, K. Kaiser, K. Issing and H. Hensel: Perception of local thermal stimuli in the course of day. Pflügers Arch 377S, R56 (1978)
488. H. J. Carlisle, C. W. Wilkinson, M. L. Laudenslager and L. D. Keith: Diurnal variation of heat intake in ovariectomized, steroid-treated rats. Horm Behav 12, 232-242 (1979)
doi:10.1016/0018-506X(79)90006-0
PMid:575715
489. E. Briese: Circadian body temperature rhythm and behavior of rats in thermoclines. Physiol Behav 37, 839-847 (1986)
doi:10.1016/S0031-9384(86)80002-6
490. C. J. Gordon: Twenty-four hour rhythms of selected ambient temperature in rat and hamster. Physiol Behav 53, 257-263 (1993)
doi:10.1016/0031-9384(93)90202-Q
491. B. Ray, H. N. Mallick and V. M. Kumar: Changes in sleep-wakefulness in medial preoptic area lesioned rats: role of thermal preference. Behav Brain Res 158, 43-52 (2005)
doi:10.1016/j.bbr.2004.08.006
PMid:15680193
492. C. J. Gordon, P. Becker and J. S. Ali: Behavioral thermoregulatory responses of single- and group-housed mice. Physiol Behav 65, 255-262 (1998)
doi:10.1016/S0031-9384(98)00148-6
493. M. Jefimow, M. Wojciechowski and E. Tegowska: Seasonal changes in the thermoregulation of laboratory golden hamsters during acclimation to seminatural outdoor conditions. Comp Biochem Physiol A 139, 379-388 (2004)
doi:10.1016/j.cbpb.2004.10.007
494. F. Aujard, M. Séguy, J. Terrien, R. Botalla, S. Blanc and M. Perret: Behavioral thermoregulation in a non human primate: effects of age and photoperiod on temperature selection. Exp Gerontol 41, 784-792 (2006)
doi:10.1016/j.exger.2006.06.001
PMid:16842958
495. Y. Terai, M. Asayama, T. Ogawa, J. Sugenoya, and T. Miyagawa: Circadian variation of preferred environmental temperature and body temperature. J Therm Biol 10, 151-156 (1985)
doi:10.1016/0306-4565(85)90019-1
496. L. Pöllmann: Circadian and circannual variations in the evaluation of thermal comfort in a constant climate. Indoor Environ 3, 145-148 (1994)
doi:10.1177/1420326X9400300308
497. H. E. Kim and H. Tokura: Effects of time of day on dressing behavior under the influence of ambient temperature fall from 30 OC to 15 OC. Physiol Behav 55, 645-650 (1994)
doi:10.1016/0031-9384(94)90039-6
498. J. A. Shoemaker and R. Refinetti: Day-night difference in the preferred ambient temperature of human subjects. Physiol Behav 59, 1001-1003 (1996)
doi:10.1016/0031-9384(95)02181-7
499. R. Refinetti: Homeostasis and circadian rhythmicity in the control of body temperature. Ann N Y Acad Sci 813, 63-70 (1997)
doi:10.1111/j.1749-6632.1997.tb51673.x
PMid:9100863
500. E. Briese: Normal body temperature of rats: the setpoint controversy. Neurosci Biobehav Rev 22, 427-436 (1998)
doi:10.1016/S0149-7634(97)00051-1
501. E. Satinoff, J. Liran and R. Clapman: Aberrations of circadian body temperature rhythms in rats with medial preoptic lesions. Am J Physiol 242, R352-R357 (1982)
502. E. Briese: Do medial preoptic lesions interfere with the set-point of temperature regulation? Brain Res Bull 23, 137-144 (1989)
doi:10.1016/0361-9230(89)90172-X
PMid:2804704
503. A. R. Osborne and R. Refinetti: Effects of hypothalamic lesions on the body temperature rhythm of the golden hamster. NeuroReport 6, 2187-2192 (1995)
doi:10.1097/00001756-199511000-00021
PMid:8595199
504. J. L. Seale and W. V. Rumpler: Synchronous direct gradient layer and indirect room calorimetry. J Appl Physiol 83, 1775-1781 (1997)
505. W. J. Hillenius and J. A. Ruben: The evolution of endothermy in terrestrial vertebrates: Who? When? Why? Physiol Biochem Zool 77, 1019-1042 (2004)
doi:10.1086/425185
PMid:15674773
506. G. C. Grigg, L. A. Beard and M. L. Augee: The evolution of endothermy and its diversity in mammals and birds. Physiol Biochem Zool 77, 982-997 (2004)
doi:10.1086/425188
PMid:15674771
507. K. R. Kattapong, L. F. Fogg and C. I. Eastman: Effect of sex, menstrual phase, and oral contraceptive use on circadian temperature rhythms. Chrobiol Int 12, 257-266 (1995)
doi:10.3109/07420529509057274
508. P. M. Fuller and C. A. Fuller: Genetic evidence for a neurovestibular influence on the mammalian circadian pacemaker. J Biol Rhythms 21, 177-184 (2006)
doi:10.1177/0748730406288148
PMid:16731657
509. E. Satinoff, S. Kent and M. Hurd: Elevated body temperature in female rats after exercise. Med Sci Sports Exerc 23, 1250-1253 (1991)
doi:10.1249/00005768-199111000-00008
Abbreviation: CRT: circadian rhythm of body temperature
Key Words: Body temperature, Circadian rhythm, Review
Send correspondence to: Prof. Roberto Refinetti, Circadian Rhythm Laboratory, University of South Carolina, 807 Hampton Street, Walterboro, SC 29488, USA, Tel: 843-549-6314, Fax: 843-549-6007, E-mail:refinetti@sc.edu