共查询到20条相似文献,搜索用时 566 毫秒
1.
F. Wollnik B. Schmidt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(3):171-182
Body temperature of five European hamsters exposed to semi-natural environmental conditions at 47° N in Southern Germany was recorded over a 1.5-year period using intraperitoneal temperature-sensitive radio transmitters. The animals showed pronounced seasonal changes in body weight and reproductive status. Euthermic body temperature changed significantly throughout the year reaching its maximum of 37.9±0.2°C in April and its minimum of 36.1±0.4°C in December. Between November and March the hamsters showed regular bouts of hibernation and a few bouts of shallow torpor. During hibernation body temperature correlated with ambient temperature. Monthly means of body temperature during hibernation were highest in November (7.9±0.8°C) and March (8.2±0.5°C) and lowest in January (4.4±0.7°C). Using periodogram analysis methods, a clear diurnal rhythm of euthermic body temperature could be detected between March and August, whereas no such rhythm could be found during fall and winter. During hibernation bouts, no circadian rhythmicity was evident for body temperature apart from body temperature following ambient temperature with a time lag of 3–5 h. On average, hibernation bouts lasted 104.2±23.8 h with body temperature falling to 6.0±1.7°C. When entering hibernation the animals cooled at a rate of -0.8±0.2°C·h-1; when arousing from hibernation they warmed at a rate of 9.9±2.4°C·h-1. Warming rates were significantly lower in November and December than in January and February, and correlated with ambient temperature (r=-0.46, P<0.01) and hibernating body temperature (r=-0.47, P<0.01). Entry into hibrnation occured mostly in the middle of the night (mean time of day 0148 hours ±3.4 h), while spontaneous arousals were widely scattered across day and night. For all animals regression analysis revealed free-running circadian rhythms for the timing of arousal. These results suggest that entry into hibernation is either induced by environmental effects or by a circadian clock with a period of 24 h, whereas arousal from hibernation is controlled by an endogenous rhythm with a period different from 24 h.Abbreviations
bw
body weight
-
CET
central European time
-
T
a
ambient temperature
-
T
b
body temperature
-
TTL
transistor-transistor logic 相似文献
2.
Thomas Waßmer Franziska Wollnik 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):270-279
Body temperature (T
b) of seven European hamsters maintained at constant ambient temperature (T
a = 8 °C) and constant photoperiod (LD 8:16) was recorded throughout the hibernating season using intraperitoneal temperature-sensitive
HF transmitters. The animals spent about 30% of the hibernation season in hypothermia and 70% in inter-bout normothermy. Three
types of hypothermia, namely deep hibernation bouts (DHBs), short hibernation bouts (SHBs), and short and shallow hibernation
bouts (SSHBs), were distinguished by differences in bout duration and minimal body temperature (T
m). A gradual development of SSHBs from the diel minimum of T
b during normothermy could be seen in individual hamsters, suggesting a stepwise decrease of the homeostatic setpoint of T
b regulation during the early hibernation season. Entry into hibernation followed a 24-h rhythm occurring at preferred times
of the day in all three types of hypothermia. DHBs and SHBs were initiated approximately 4 h before SSHBs, indicating a general
difference in the physiological initiation of SSHBs on the one hand and DHBs and SHBs on the other. Arousals from SHBs and
SSHBs also followed a 24-h rhythm, whereas spontaneous arousals from DHBs were widely scattered across day and night. Statistical
analyses of bout length and the interval between arousals revealed evidence for a free-running circadian rhythm underlying
the timing of arousals. The results clearly demonstrate that entries into hypothermia are linked to the light/dark-cycle.
However, the role of the circadian system in the timing of arousals from DHBs remains unclear.
Accepted: 11 December 1996 相似文献
3.
F. Geiser L. S. Broome 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):133-137
Physiological variables of torpor are strongly temperature dependent in placental hibernators. This study investigated how changes in air temperature affect the duration of torpor bouts, metabolic rate, body temperature and weight loss of the marsupial hibernator Burramys parvus (50 g) in comparison to a control group held at a constant air temperature of 2°C. The duration of torpor bouts was longest (14.0±1.0 days) and metabolic rate was lowest (0.033±0.001 ml O2·g-1·h-1) at2°C. At higher air temperatures torpor bouts were significantly shorter and the metabolic rate was higher. When air temperature was reduced to 0°C, torpor bouts also shortened to 6.4±2.9 days, metabolic rate increased to about eight-fold the values at 2°C, and body temperature was maintained at the regulated minimum of 2.1±0.2°C. Because air temperature had such a strong effect on hibernation, and in particular energy expenditure, a change in climate would most likely increase winter mortality of this endangered species.Abbreviationst STP
standard temperature and pressure
-
T
a
air temperature
-
T
b
body temperature
-
VO2
rate of oxygen consumption 相似文献
4.
El Ouezzani S Janati IA Magoul R Pévet P Saboureau M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(2):299-309
The jerboa (Jaculus orientalis) has been described in the past as a hibernator, but no reliable data exist on the daily and seasonal rhythmicity of body
temperature (T
b). In this study, T
b patterns were determined in different groups of jerboas (isolated males and females, castrated males and grouped animals)
maintained in captivity during autumn and winter, and submitted to natural variations of light and ambient temperature (T
a). T
b and T
a variations were recorded with surgically implanted iButton temperature loggers at 30-min intervals for two consecutive years.
About half (6/13) of isolated female jerboas hibernated with a T
b < 33°C, with hibernation bouts interspersed with short periods of normothermy from November to February. Hibernation bout
durations were longer (4–5 days) than those of normothermia phases (1–4 days). During hibernation, the minimum T
b was low (T
bmin ~10.7°C). In contrast, one of the 12 isolated males showed short hibernation bouts of ca. 2 days late in the hibernation
season, February–March. The males had T
bmin values of 15.1°C. In contrast to predictions, no castrated males hibernated. When jerboas were grouped, females and males
exhibited concomitant torpor bouts. In males, the longest bouts were observed during the late hibernation season. These data
suggest complex regulation of hibernation in jerboas. 相似文献
5.
Comparison of hibernation, estivation and daily torpor in the edible dormouse, Glis glis 总被引:2,自引:0,他引:2
Wilz M Heldmaier G 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(7):511-521
Three major forms of dormancy in mammals have been classified: hibernation in endotherms is characterised by reduced metabolic
rate (MR) and body temperature (T
b) near ambient temperature (T
a) over prolonged times in the winter. Estivation is a similar form of dormancy in a dry and hot environment during summertime.
Daily torpor is defined as reduced MR and T
b lower than 32 °C, limited to a duration of less than 24 h. The edible dormouse (Glis glis) is capable for all three distinct forms of dormancy. During periods of food restriction and/or low T
a, daily torpor is displayed throughout the year, alternating with hibernation and estivation in winter and summer respectively.
We recorded T
b, O2-consumption and CO2-production in unrestrained dormice at different T
a's for periods of up to several months. Cooling rate and rate of metabolic depression during entrance into the torpid state
was identical in all three forms of dormancy. The same was true for thermal conductance, maximum heat production, duration
of arousal and cost of an arousal. The only difference between hibernation and daily torpor was found in the bout duration.
A daily torpor bout lasted 3–21 h, a hibernation bout 39–768 h. As a consequence of prolonged duration, MR, T
b and also the T
b − T
a gradient decreased to lower values during hibernation bouts when compared to daily torpor bouts. Our findings suggest that
all three forms of dormancy are based on the same physiological mechanism of thermal and metabolic regulation.
Accepted: 27 June 2000 相似文献
6.
Walter Arnold 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(2):151-156
Summary Body temperature (T
b) of socially hibernating alpine marmots, a pair and two family groups, was monitored continuously from October to March with implanted temperature-sensitive radiotransmitters. At the same time, the animals' behaviour was observed. The recurrent entrances into and arousals from hibernation were highly synchronised within groups. Group members always lay huddled together when euthermic and also when torpid with a few exceptions at higher ambient temperatures (T
a). Body contact with euthermic nestmates warmed torpid marmots passively. TheT
b of animals reentering hibernation did not fall to values close toT
a as long as euthermic group members were present. Although animals presumably save energy through social thermoregulation, especially when euthermic, these benefits are not necessarily mutual among group members. Differences in thermoregulatory behaviour of individuals described in this study could be responsible for differential weight losses during winter as found in the natural habitat (Arnold 1986). 相似文献
7.
B. Canguilhem A. Malan M. Masson-Pévet P. Nobelis R. Kirsch P. Pévet J. Le Minor 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,163(8):690-698
Temporal patterns of hibernation were studied by continuous monitoring of body temperature by radiotelemetry over 6 months in European hamsters, Cricetus cricetus, at constant temperature and photoperiod. Entrances into hibernation occurred mostly at the end of the night (0000–0800 hours), while arousals were randomly distributed between day and night. This is at variance with a control of bout duration by a clock with a period of 24 h. Consequently, the timing of entrances implies a phase-resetting of the circadian clock on each arousal. Persistence of circadian rhythmicity with a period different from 24 h during deep hibernation was investigated examining whether the durations of torpor bouts were integer multiples of a constant period. A non-parametric version of the classical contingency test of periodicity was developed for this purpose. Periods ranging from 21 to 29 h were tested. Nine animals out of ten showed at least one significant period in this range (P<0.01), either below 24 h (21.8±0.5 h, n=4) or above (27.3±0.5 h, n=7). However, we have found a theoretical model of bout durations for which the contingency test of periodicity sometimes gives false significant results. This indicates that the power of the test is weak. With this reservation our results suggest that a circadian oscillator controls the duration of a bout of hibernation, which would occur after an integer, but variable and possibly temperature-dependent number of cycles.Abbreviations b
a contingency test (see Appendix)
- SCN
suprachiasmatic nuclei
-
period
-
T
b
body temperature 相似文献
8.
《Chronobiology international》2013,30(4):879-887
Subterranean common mole voles, Ellobius talpinus, were implanted with long-term recording electronic thermometers to obtain hourly body temperature (Tb) data during either the wintertime or summertime. The two individuals tested during the summertime had significant circadian and ultradian rhythms in their Tb. Four of the five mole voles tested during the wintertime lacked rhythmicity in their Tb. The fifth individual lacked circadian rhythms but had ultradian rhythms in its Tb. A loss of circadian rhythms in Tb during deep torpor or hibernation has been reported for a few species of mammals. Inasmuch as the mole voles' wintertime Tb remained at euthermic levels, our results show that a loss of circadian body temperature rhythms in mole voles does not require the low Tb of deep torpor or hibernation. A tentative conclusion, based on these few animals, is that in common mole voles the Tb rhythms may disappear during the wintertime even though their Tb remains high. (Author correspondence: eug_nov@ngs. ru) 相似文献
9.
Razi Dmi'el Miriam Schwarz 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1984,155(1):117-123
Summary Hibernation patterns, body temperature (T
b) and oxygen consumption (
) were measured during hibernation in two hedgehog species, a desert speciesHemiechinus auritus (body mass 367 g) and a temperate habitat speciesErinaceus europaeus (body mass 598 g). A continuous ambient temperature of 11 °C was the only necessary condition for both species to enter hibernation outdoors and in the laboratory. At this temperature, hibernation could be induced at any time of the year. Hibernation bouts ofHemiechinus were regular and short (average 4.8 days), whereas those ofErinaceus lasted 5 to 27 days (average 9.3 days). The frequency of spontaneous arousals was 5.3 and 2.9 per month forHemiechinus andErinaceus, respectively. None of the hedgehogs took any food during arousal periods. Both species had the sameT
b during hibernation (12.5 °C) and during arousal (33 °C).
of the hibernatingHemiechinus was twice the rate ofErinaceus (0.050 vs. 0.025 ml g–1 h–1), but during arousal it was the same for both. The monthly average energy expenditure for both species was 1,477 kJ per animal, which is 15% of the energy used by non-hibernating hedgehogs. The corresponding amount of fat catabolized was 37 g per month. This mass loss would limit the hibernation inHemiechinus to 3.9 months and inErinaceus to 6.5 months. Although hibernation inHemiechinus does not constitute a special adaptation to hot environments, it significantly improves the hedgehog's energy economy during the desert winter. 相似文献
10.
The degree of dietary fatty acid unsaturation affects torpor patterns and lipid composition of a hibernator 总被引:6,自引:2,他引:4
F. Geiser B. M. McAllan G. J. Kenagy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(4):299-305
Diets rich in unsaturated and polyunsaturated fatty acids have a positive effect on mammalian torpor, whereas diets rich in saturated fatty acids have a negative effect. To determine whether the number of double bonds in dietary fatty acids are responsible for these alterations in torpor patterns, we investigated the effect of adding to the normal diet 5% pure fatty acids of identical chain length (C18) but a different number of double bonds (0, 1, or 2) on the pattern of hibernation of the yellow-pine chipmunk, Eutamias amoenus. The response of torpor bouts to a lowering of air temperature and the mean duration of torpor bouts at an air temperature of 0.5°C (stearic acid C18:0, 4.5±0.8 days, oleic acid C18:1, 8.6±0.5 days; linoleic acid C18:2, 8.5±0.7 days) differed among animals that were maintained on the three experimental diets. The mean minimum body temperatures (C18:0, +2.3±0.3°C; C18:1, +0.3±0.2°C; C18:2,-0.2±0.2°C), which torpid individuals defended by an increase in metabolic rate, and the metabolic rate of torpid animals also differed among diet groups. Moreover, diet-induced differences were observed in the composition of total lipid fatty acids from depot fat and the phospholipid fatty acids of cardiac mitochondria. For depot fat 7 of 13 and for heart mitochondria 7 of 14 of the identified fatty acids differed significantly among the three diet groups. Significant differences among diet groups were also observed for the sum of saturated, unsaturated and polyunsaturated fatty acids. These diet-induced alterations of body fatty acids were correlated with some of the diet-induced differences in variables of torpor. The results suggest that the degree of unsaturation of dietary fatty acids influences the composition of tissues and membranes which in turn may influence torpor patterns and thus survival of hibernation.Abbreviations bm
body mass
-
T
a
air temperature
-
T
b
body temperature
- FA
fatty acid
- MR
metabolic rate
- MUFA
monounsaturated fatty acids
- PUFA
polyunsaturated fatty acids
-
VO2
rate of oxygen consumption
- SFA
saturated fatty acids
- UFA
unsaturated fatty acids
- UI
unsaturation index
- SNK
Student-Newman-Keuls test 相似文献
11.
Mariska Batavia George Nguyen Kristine Harman Irving Zucker 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2013,183(2):269-277
Turkish hamsters (Mesocricetus brandti) are a model organism for studies of hibernation, yet a detailed account of their torpor characteristics has not been undertaken. This study employed continuous telemetric monitoring of body temperature (T b) in hibernating male and female Turkish hamsters at ambient temperatures (T as) of 5 and 13 °C to precisely characterize torpor bout depth, duration, and frequency, as well as rates of entry into and arousal from torpor. Hamsters generated brief intervals of short (<12 h), shallow test bouts (T b > 20 °C), followed by deep torpor bouts lasting 4–6 days at T a = 5 °C and 2–3 days at T a = 13 °C. Females at T a = 5 °C had longer bouts than males, but maintained higher torpor T b; there were no sex differences at T a = 13 °C. Neither body mass loss nor food intake differed between the two T as. Hamsters entered torpor primarily during the scotophase (subjective night), but timing of arousals was highly variable. Hamsters at both T as generated short, shallow torpor bouts between deep bouts, suggesting that this species may be capable of both hibernation and daily torpor. 相似文献
12.
M. D. McArthur C. C. Hanstock A. Malan L. C. H. Wang P. S. Allen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(4):339-347
Summary The time-course of changes in skeletal muscle pH during arousal from hibernation in the Columbian ground squirrel was studied using31P NMR spectroscopy. In hibernation (T
re 7–9°C), shoulder/neck muscle pH was 7.45±0.03 and Im was 0.60. In euthermia (T
re 37°C), muscle pH was 7.24±0.05 and Im was 0.75. Thus the overall pH-temperature coefficient was-0.009 pH units/°C, indicating acidification of the muscle in hibernation. During the transition from hibernation to euthermia, however, the muscle shows a nonlinear pattern of pH change. In early arousal (T
sh<20–25°C,T
re<15°C) muscle pH does not change and muscle Im increases to 0.72. In later arousal (T
sh>20–25°C,T
re>15°C) muscle pH decreases gradually toward the euthermic value and muscle Im increases only slightly from 0.72 to 0.75. These results support the hypothesis that intracellular acidification of the muscle, present during hibernation, is reversed in early arousal. This may facilitate an increase in muscle metabolism and the contribution of maximal shivering thermogenesis to rewarming of the animal.Abbreviations Im
dissociation ratio of protein imidazole buffergroups
-
NST
non-shivering thermogenesis
-
BAT
brown adipose tissue
-
dp H/dT
temperature coefficient of pH
-
pH
i
intracellular pH
-
31
P NMR
31Phosphorus nuclear magnetic resonance
- P
i
chemical shift of inorganic phosphate relative to PCr
-
PCr
phosphocreatine
-
T
b
body temperature
-
T
re
rectal temperature
-
T
sh
subcutaneous shoulder temperature
-
T
a
ambient temperature 相似文献
13.
《Chronobiology international》2013,30(2):103-128
Mammals and birds have evolved the ability to maintain a high and constant body temperature Tb over a wide range of ambient temperatures Ta using endogenous heat production. In many, especially small endotherms, cost for thermoregulatory heat production can exceed available energy; to overcome these energetic bottlenecks, they enter a state of torpor (a regulated reduction of Tb and metabolic rate). Since the occurrence of torpor in many species is a seasonal event and occurs at certain times of the day, we review whether circadian and circannual rhythms, important in the timing of biological events in active animals, also play an important role during torpor when Tb is reduced substantially and may even fall below 0°C. The two distinct patterns of torpor, hibernation (prolonged torpor) and daily torpor, differ substantially in their interaction with the circadian system. Daily torpor appears to be integrated into the normal circadian rhythm of activity and rest, although torpor is not restricted only to the normal rest phase of an animal. In contrast, hibernation can last for several days or even weeks, although torpor never spans the entire hibernation season, but is interrupted by periodic arousals and brief normothermic periods. Clearly, a day is no longer divided in activity and rest, and at first glance the role of the circadian system appears negligible. However, in several hibernators, arousals not only follow a regular pattern consistent with a circadian rhythm, but also are entrainable by external stimuli such as photoperiod and Ta. The extent of the interaction between the circadian and circannual system and hibernation varies among species. Biological rhythms of hibernators for which food availability appears to be predictable seasonally and that hibernate in deep and sealed burrows show little sensitivity to external stimuli during hibernation and hence little entrainability of arousal events. In contrast, opportunistic hibernators, which some times use arousals for foraging and hibernate in open and accessible hibernacula, are susceptible to external zeitgebers. In opportunistic hibernators, the circadian system plays a major role in maintaining synchrony between the normal day-night cycle and occasional foraging. Although the daily routine of activity and rest is abandoned during hibernation, the circadian system appears to remain functional, and there is little evidence it is significantly affected by low Tb. (Chronobiology International, 17(2), 103–128, 2000) 相似文献
14.
Heterothermy in the southern African hedgehog, <Emphasis Type="Italic">Atelerix frontalis</Emphasis>
Hallam SL Mzilikazi N 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(3):437-445
Most research on mammalian heterothermic responses in southern Africa tends to be laboratory based and biased towards rodents
and smaller members of the Afrotheria. In this study, we continuously measured body temperature of southern African hedgehogs
(Atelerix frontalis) between April and August 2009 (−10°C < T
a < 43°C), kept under semi-captive conditions. A. frontalis showed a high propensity for torpor with animals spending up to 84% of the measurement period torpid. During this study,
A. frontalis displayed the lowest T
b min (ca 1°C) yet recorded in an Afrotropical placental heterotherm. Bout lengths of between 0.7 h (40 min) and 116.3 h (4.8 days)
were recorded. Differences in bout length were observed between lighter individuals compared with an individual exhibiting
a higher body mass at the onset of winter, with low M
b individuals exhibiting daily torpor whereas a heavier individual exhibited torpor bouts that were indicative of hibernation.
Our results suggest that heterothermic responses are an important feature in the energy balance equation of this species and
that body mass at the onset of winter may determine the patterns of heterothermy utilised in this species. 相似文献
15.
The hibernating marsupial mountain pygmy-possum (Burramys parvus, 40 g) has to raise its slow-growing offspring during a short alpine summer. Only females provide parental care, while after
mating males emigrate to marginal habitats often at lower altitudes which can sustain only low possum densities. We predicted
that the hibernation strategies in mountain pygmy-possums are distinct from those of similar-sized placental hibernators,
because of the developmental constraints in marsupials and because hibernation differs between the sexes. Using temperature-sensitive
radio transmitters, we studied the hibernation patterns of free-living male and female mountain pygmy-possums living in a
north- and a south-facing boulder field (Kosciusko National Park) for two consecutive winters. Individual possums commenced
hibernation several months before the snow season. As in other hibernators, torpor in the mountain pygmy-possum was interrupted
by periodic arousals which occurred most often during the late afternoon. Torpor bouts initially lasted a few days when the
hibernacula temperature (T
hib) ranged from 4 to 7°C. As the hibernation season progressed, torpor bouts became longer and possum body temperatures (T
b) approached 2°C. The T
bs of females were significantly lower and torpor bouts were longer in the second half of the hibernation season than in males.
Between torpor bouts, both sexes were often active and left hibernacula for periods of up to 5 days. Especially during the
first months of the hibernation season, possums also frequently changed hibernacula sites probably in an attempt to select
a site with a more suitable microclimate. Emergence from hibernation was closely coupled with the disappearance of snow from
the possum habitat (September 1995, October 1996) and the limited fat stores probably dictate an opportunistic spring emergence.
However, in 1995, spring was early and males emerged significantly earlier than females. In 1996, when snow melt was delayed,
this difference vanished. Testes are regressed in males during hibernation and the time needed for testes growth and spermatogenesis
favours an earlier emergence for males which was probably achieved by their preference for the more sun exposed north-facing
boulder field. A sexual dimorphism in hibernation strategies and spring emergence therefore enables mountain pygmy-possums
to cope with their harsh alpine environment.
Received: 22 May 1997 / Accepted: 21 August 1997 相似文献
16.
Williams CT Sheriff MJ Schmutz JA Kohl F Tøien Ø Buck CL Barnes BM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(8):1101-1109
Precise measures of phenology are critical to understanding how animals organize their annual cycles and how individuals and
populations respond to climate-induced changes in physical and ecological stressors. We show that patterns of core body temperature
(T
b) can be used to precisely determine the timing of key seasonal events including hibernation, mating and parturition, and
immergence and emergence from the hibernacula in free-living arctic ground squirrels (Urocitellus parryii). Using temperature loggers that recorded T
b every 20 min for up to 18 months, we monitored core T
b from three females that subsequently gave birth in captivity and from 66 female and 57 male ground squirrels free-living
in the northern foothills of the Brooks Range Alaska. In addition, dates of emergence from hibernation were visually confirmed
for four free-living male squirrels. Average T
b in captive females decreased by 0.5–1.0°C during gestation and abruptly increased by 1–1.5°C on the day of parturition. In
free-living females, similar shifts in T
b were observed in 78% (n = 9) of yearlings and 94% (n = 31) of adults; females without the shift are assumed not to have given birth. Three of four ground squirrels for which
dates of emergence from hibernation were visually confirmed did not exhibit obvious diurnal rhythms in T
b until they first emerged onto the surface when T
b patterns became diurnal. In free-living males undergoing reproductive maturation, this pre-emergence euthermic interval averaged
20.4 days (n = 56). T
b-loggers represent a cost-effective and logistically feasible method to precisely investigate the phenology of reproduction
and hibernation in ground squirrels. 相似文献
17.
G. Heldmaier T. Ruf 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(8):696-706
During daily torpor and hibernation metabolic rate is reduced to a fraction of the euthermic metabolic rate. This reduction is commonly explained by temperature effects on biochemical reactions, as described by Q
10 effects or Arrhenius plots. This study shows that the degree of metabolic suppression during hypothermia can alternatively be explained by active downregulation of metabolic rate and thermoregulatory control of heat production. Heat regulation is fully adequate to predict changes in metabolic rate, and Q
10 effects are not required to explain the reduction of energy requirements during hibernation and torpor.Abbreviations BMR
basal metabolic rate
- BW
body weight
- C
thermal conductance
- CHL
thermal conductance as derived from HL
- CHP
thermal conductance as derived from HP
- HL
heat loss
- HP
heat production
- MR
metabolic rate
- RQ
respiratory quotient
- Ta
ambient temperature
- Tb
body temperature 相似文献
18.
Kart Gür M Refinetti R Gür H 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(2):155-164
We studied daily rhythmicity of body temperature (T
b) before and during hibernation in Anatolian ground squirrels (Spermophilus xanthoprymnus) under natural and laboratory conditions using surgically implanted temperature loggers. Under both conditions, robust daily
T
b rhythmicity with parameters comparable to those of other ground squirrel species was observed before but not during hibernation.
Euthermic animals had robust daily T
b rhythms with a mean of 37.0°C and a range of excursion of approximately 4°C. No T
b rhythm was detected during torpor bouts, either because T
b rhythmicity was absent or because the daily range of excursion was smaller than 0.2°C. The general patterns of hibernation
that we observed in Anatolian ground squirrels were similar to those previously observed by other investigators in other species
of ground squirrels. 相似文献
19.
Séguy M Perret M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(2):107-115
Microcebus murinus, a small nocturnal Malagasy primate, exhibits adaptive energy-saving strategies such as daily hypothermia and gregarious patterns during diurnal rest. To determine whether ambient temperature (Ta), food restriction and nest sharing can modify the daily body temperature (Tb) rhythm, Tb was recorded by telemetry during winter in six males exposed to different ambient temperatures (Ta=25, 20, 15°C) and/or to a total food restriction for 3 days depending on social condition (isolated versus pair-grouped). At 25°C, the daily rhythm of Tb was characterized by high Tb values during the night and lower values during the day. Exposure to cold significantly decreased minimal Tb values and lengthened the daily hypothermia. Under food restriction, minimal Tb values were also markedly lowered. The combination of food restriction and cold induced further increases in duration and depth of torpor bouts, minimal Tb reaching a level just above Ta. Although it influenced daily hypothermia less than environmental factors, nest sharing modified effects of cold and food restriction previously observed by lengthening duration of torpor but without increasing its depth. In response to external conditions, mouse lemurs may thus adjust their energy expenditures through daily modifications of both the duration and the depth of torpor. 相似文献
20.
Juliet R. Roberts R. V. Baudinette 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(2):205-211
Summary Stubble quail and King quail are both native to Australia although Stubble quail extend into more arid environments than do King quail. In this study, the responses of body temperature (T
b), heart rate (f
h), respiration rate (f
r) and rates of gular flutter (f
g) were measured in response to ambient temperatures (T
a) ranging from 20 °C to 50 °C. Both species exhibited hyperthermia atT
a in excess of 38–39 °C although both species maintainedT
b lower thanT
a atT
a above 42 °C. Respiration rate remained relatively constant until the onset of panting, just prior to the commencement of gular flutter. The onset of panting and gular flutter in both species was relatively sudden and occurred at a meanT
a of 38.1 °C for Stubble quail (meanT
b of 42.5 °C) and a significantly higherT
a of 40.9 °C but similar meanT
b of 42.1 °C for King quail. Gular flutter appeared to occur synchronously with respiration and showed some tendency to increase withT
b. The percentage of time spent in gular flutter showed a direct increase withT
b. Heart rate tended to decrease with increasingT
a in King quail while remaining relatively constant in Stubble quail. However, the relationship was not consistent and a great deal of variability existed between individuals. The two species are similar in their responses to heat stress and in general these responses do not reflect their different natural habitats.Symbols
f
h
heart rate
-
f
r
respiratory rate
-
f
g
rate of gular fluttering 相似文献