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1.
2.
《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
3.
Daily and seasonal cycles of body temperature and aspects of heterothermy in the hedgehog Erinaceus europaeus 总被引:1,自引:1,他引:0
P. A. Fowler P. A. Racey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(3):299-307
Summary Intra-abdominal temperature-sensitive radio transmitters were used to collect more than 350 sets of body temperature (T
b
) data from 23 captive adult hedgehogs over a 3-year period. Each data set comprised measurements made every 1/2 h for 24-h periods. Between 20 and 60 such data sets were recorded every calendar month, and a total of 17400 measurements of T
b
were collected. The hedgehogs were exposed to natural environmental conditions at 57°N in NE Scotland. Hedgehogs showed seasonal changes in mean daily euthermic T
b
,with a July maximum of 35.9±0.2°C, a September minimum of 34.7±0.9°C, and a marked circadian T
b
cycle that correlates closely with photoperiod. Maximal T
b
occurred within 2 h of midnight and this pattern of nocturnal maximum and diurnal minimum T
b
was most marked between April and September. The circadian T
b
cycle was least correlated with photoperiod during winter. Hibernal T
b
during winter correlated with ambient temperature (T
a
),it was maximal in September (17.7±1.0°C) and minimal in December (5.2±0.9°C). Apart from the tracking of T
a
and T
b
during hibernal bouts, with a time-lag of 4–6 h, circadian rhythmicity of hibernal T
b
was not evident. However, the T
b
of hibernating hedgehogs rose significantly when T
a
fell below — 5°C, although the animals did not neccessarily arouse. Although hibernal bouts occurred between September and April, 89.5% of such bouts were recorded between November and February. The mean time of entry into hibernation was 01:45±5.1 h GMT while the mean time of the start of spontaneous arousal from hibernation was 11:53±4.8 h GMT. Therefore, during hibernation hedgehogs were either fully aroused at night, when euthermic hedgehogs have maximalT
b
,or in deep hibernation around midday, when euthermic hedgehogs have minimal T
b
.Since wild hedgehogs will feed during spontaneous arousal from hibernation, these timings are probably adaptive, and suggest that entry into, and arousal from, hibernation may be extensions of circadian cyclicity. Spontaneous bouts of transient shallow torpor (TST) were recorded throughout the year, with nearly 80% of observations occurring during August and September, at the start of the hibernal period. TST bouts lasted for 4.9±2.9 h, with T
b
falling to 25.8±3.1 °C. Only 20% of TST bouts immediately preceded hibernation and their duration did not correlate with T
a
or body mass. TST bouts started at 06:51±4.7 h GMT, significantly later than entry into hibernation, and ended at 13:04±5.4 h GMT. The function of TST bouts is unclear, but they may be preparation for the hibernation season or a further energy conservation strategy. When arousing from hibernation hedgehogs warmed at a rate of 1.9±0.4°C·h-1, and when entering hibernation cooled at 7.9±1.9°C·h-1. Warming rates were slightly higher during mid-winter when T
b
and body mass were minimal, but cooling rates were 44% higher at the end of the hibernal period compared to the start. Cooling and warming rates were strikingly similar to those measured in hedgehogs at 31°N. These results demonstrate that thermoregulation in the hedgehog is closely regulated and changes on a seasonal basis, in meeting with requirements of surviving food shortages and low temperature during winter.Abbreviations
T
a
ambient temperature
-
T
b
body temperature
-
CSD
circular standard deviation
-
SWS
slow wave sleep
-
TST
transient shallow torpor 相似文献
4.
Objective: To assess the relationship between marriage and obesity. Research Methods and Procedures: Cross‐sectional and longitudinal associations were examined between participant body mass index (BMI), spouse BMI, and participant diet and exercise habits. Results: Spouse and participant BMI and BMI changes over 2 years were significantly associated. Participant BMI was associated with higher consumption of calorie‐dense foods and lower frequency of physical activity. Participants’ eating and exercise habits were only weakly related to spouse BMI. BMI did not predict the likelihood of marriage or divorce. However, marriage was associated with a significant 2‐year weight gain and divorce with a significant 2‐year weight loss. Discussion: The results suggest that spouse similarity in BMI is at least partly due to shared environment. The observed effects of marriage and divorce on weight may be due to the influence of marriage on inducements to eat (e.g., shared meals) or on motivation for weight control. 相似文献
5.
M. A. Chappell 《Oecologia》1981,49(3):397-403
Summary Body temperatures (T
b) and daily activity patterns of free-living arctic ground squirrells (Spermophilus undulatus) were determined via telemetry at a field site in northern Alaska. Simultaneous measurements were made of ambient temperature (T
a), wind speed (V), and incident solar radiation. The operative environmental temperature (T
e) for ground squirrels was obtained from fur-covered, thin metal taxidermic models of the animals. Standard operative temperature (T
es), a comparative index of heat flow, was calculated from T
e, V, and laboratory measurements of thermal conductivity.During the period of the study (August), S. undulatus were active for about 14 h per day (06.00 to 20.00 h). T
b was high throughout the daily cycle, averaging 38–39°C. Circadian variations in T
b were slight; average T
b values dropped <1°C at night. Daytime T
b fluctuations were not closely correlated to activity or to changes in environmental conditions. Air temperatures during the study were low, usually between 10 and 15°C during the day. However, T
es in exposed areas was normally higher, even though skies were generally overcast. During periods of sunshine, T
es may be as high as 34°C. The absence of nocturnal activity may result from increased costs of thermoregulation at night, which sharply reduces foraging efficiency. The high and stable body temperatures of S. undulatus probably result from thermoneutral daytime T
es, low activity levels, and the use of well-insulated nests. 相似文献
6.
Fritz Geiser Bruce T. Firth Roger S. Seymour 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(1):1-4
Summary Cold acclimation lowers the selected body temperature (T
b) in many ectothermic vertebrates. This change in behavioural thermoregulation is accompanied by an increase in the proportion of polyunsaturated fatty acids in tissues and cellular membranes. We investigated how diets containing different fatty acids, known to significantly alter the fatty acid composition of animal tissues and membranes, affect the selected T
b of the lizard Tiliqua rugosa. Lizards on a diet containing many polyunsaturated fatty acids (10% sunflower oil) showed a 3–5°C decrease in T
b, whereas T
b in animals on a diet containing mainly saturated fatty acids (10% sheep fat) did not change. Our study suggests that the composition of dietary lipids influences thermoregulation in ectothermic vertebrates and may thus play a role in the seasonal adjustment of their physiology.Abbreviations CST
central standard time
-
T
a
air temperature
-
T
b
Body temperature 相似文献
7.
《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
8.
F. Aujard M. Perret G. Vannier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(7):540-548
The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food
availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal
rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in
ambient temperature, evaporative water loss (EWL), body temperature (T
b) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging
from 5 °C to 35 °C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions.
In both photoperiods, EWL, T
b and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 °C was associated
with a decrease in T
b and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in T
b and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed
according to daylength. Daily variations in T
b and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase
of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of T
b decrease with or without the occurrence of torpor (T
b < 33 °C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory
processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations.
Accepted: 4 August 1998 相似文献
9.
Evaluation of two methods for minimally invasive peripheral body temperature measurement in birds
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Andreas Nord Marina Lehmann Ross MacLeod Dominic J. McCafferty Ruedi G. Nager Jan‐Åke Nilsson Barbara Helm 《Journal of avian biology》2016,47(3):417-427
Body temperature (Tb) is a valuable parameter when assessing the physiological state of animals, but its widespread measurement is often constrained by methods that are invasive or require frequent recapture of animals. Alternatives based on automated remote sensing of peripheral Tb show promise, but little is known about their strengths and limitations. We measured peripheral Tb in great tits Parus major with subcutaneously implanted passive integrated transponders (PIT tags) and externally attached radio transmitters to determine repeatability of measurements, sensitivity of each method to variation in ambient temperature (Ta) and wind speed, the relationship between methods, and their ability to capture circadian variation in Tb. Repeatability of measurements by radio transmitters was high (> 80%) when readings were taken within 20 min, but reduced to 16% when measures were spaced 3.5 h apart. PIT tag data for the 3.5 h interval were more repeatable (33%) and less variable (cv). Data were affected by Ta with a stronger effect on the externally attached transmitters, but the influence of wind speed was small for both methods. There was a significant positive relationship between transmitter‐ and PIT tag temperature during both days and nights. Both methods were equally suited to detect diel changes in peripheral Tb. However, transmitters offered longer detection distance and better temporal resolution. These qualities should be considered when deciding how to collect Tb data remotely. If properly deployed, both methods allow measurement of peripheral Tb over a wide range of natural systems and conditions in small, free‐ranging, birds. 相似文献
10.
The aim of this study was to investigate the variations in plasma triiodothyronine (T3) and thyroxine (T4) with the advancement of age and to determine their circadian patterns in prepubertal and pubertal Murrah buffaloes. The variations in plasma T3 and T4 with the advancement of age were observed from day 1 to 24 months of age. Significant higher levels of T3 and T4 were observed after birth and a gradual decrease in their concentrations occurred until 15 days of age. The mean plasma T3 and T4 ranged between 1.26–3.79 and 60.7–166 ng/ml, respectively, during 1–30 days of age. During 1–24 months of age, the variations in plasma T3 did not differ (p > 0.05) with the advancement of age, whereas significant (p < 0.0001) changes were observed in plasma T4. The circadian patterns of T3 and T4 were evaluated in prepubertal Murrah buffaloes (n = 8) aged between 14 and 16 months. The mean plasma T3 and T4 ranged between 1.04–1.85 and 43.0–76.1 ng/ml, respectively. Significant (p > 0.0001) changes in the secretory pattern of T3 were observed, whereas the secretory pattern of T4 did not differ significantly (p > 0.05). In addition, the circadian patterns of T3 and T4 in pubertal buffaloes (n = 4) aged between 28 and 30 months were observed and compared to that of prepubertal group (n = 4). The prepubertal group showed significant (p < 0.001) higher plasma T3 concentrations over 24 h than the pubertal group. 相似文献
11.
Ben-Hamo M McCue MD McWilliams SR Pinshow B 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(6):807-816
Many avian species reduce their body temperature (T
b) to conserve energy during periods of inactivity, and we recently characterized how ambient temperature (T
a) and nutritional stress interact with one another to influence physiologically controlled hypothermic responses in Japanese
quail (Coturnix japonica). In the present study, we examined how the fatty acid (FA) composition of the diet influences the FA composition of phospholipids
in major organs and how these affect controlled hypothermic responses and metabolic rates in fasted birds. For 5 weeks prior
to fasting, quail were fed a standard diet and gavaged each morning with 0.7 ml of water (control), or a vegetable oil comprising
saturated fatty acids (SFA; coconut oil), or unsaturated fatty acids (UFA; canola oil). Birds were then fasted for 4 days
at a T
a of 15°C. We found that, while fasting, both photophase and scotophase T
b decreased significantly more in the SFA treatment group than in the control group; apparently the former down-regulated their
T
b set point. This deeper hypothermic response was correlated with changes in the phospholipid composition of the skeletal muscle
and liver, which contained significantly more oleic acid (18:1) and less arachidonic acid (20:4), respectively. Our data imply
that these two FAs may be associated with thermoregulation. 相似文献
12.
Basal metabolic rate (BMR) of birds is beginning to be viewed as a highly flexible physiological trait influenced by environmental fluctuations, and in particular changes in ambient temperatures (Ta). Southern Africa is characterized by an unpredictable environment with daily and seasonal variation. This study sought to evaluate the effects of seasonal changes in Ta on mass-specific resting metabolic rate (RMR), BMR and body temperature (Tb) of Red-winged Starlings (Onychognathus morio). They have a broad distribution, from Ethiopia to the Cape in South Africa and are medium-sized frugivorous birds. Metabolic rate (VO2) and Tb were measured in wild caught Red-winged Starlings after a period of summer and winter acclimatization in outdoor aviaries. RMR and BMR were significantly higher in winter than summer. Body mass of Starlings was significantly higher in winter compared with summer. The increased RMR and BMR in winter indicate improved ability to cope with cold and maintenance of a high Tb. These results show that the metabolism of Red-winged Starlings are not constant, but exhibit a pronounced seasonal phenotypic flexibility with maintenance of a high Tb. 相似文献
13.
《Chronobiology international》2013,30(6):949-960
The eating habits of workers may vary according to the season of the year and corresponding work schedule. A study aiming at verifying the changes in their diet in summer and winter, as well as the nutritional status of those who work fixed shifts, was conducted. The distribution during the 24 h in the quantity of calories and macronutrients ingested and the circadian rhythm of calories consumed were also analyzed. The study was conducted on 28 workers subject to three fixed work (morning, afternoon, and night) shifts at a transport company in the city of São Paulo, Brazil. The mean age of the workers was 32.8 (SD ± 5.3) yrs. Their food intake was ascertained by the use of a 3-day dietary record, and their nutritional status was evaluated by their body mass index (BMI), both in winter and summer. Two-way ANOVA (shift and season) showed food consumption—measured in calories/24 h—was significantly higher in winter than summer (F(1.25) = 11.7; p < 0.001). No statistically significant differences were found among shifts (F(2.25) = 0.85; p < 0.44), and the interaction effect between shift and season was also not significant (F(2.25) = 0.15; p < 0.86). No seasonal difference in BMI was detected (Kruskal-Wallis test). Cosinor analyses showed circadian rhythmicity in calories consumed by morning (p < 0.01) as well as afternoon shift workers (p < 0.001), both in the winter and summer. Circadian rhythmicity in calories consumed by night workers was found only in summer (p < 0.01). The changes observed in the workers’ eating habits from one season to another and during the 24 h period show the need for further studies to help develop educational programs to improve the nutrition of shift employees taking into consideration shift schedule and season of the year when work is performed. 相似文献
14.
Birds commonly use rest-phase hypothermia, a controlled reduction of body temperature (T
b), to conserve energy during times of high metabolic demands. We assessed the flexibility of this heterothermic strategy by
increasing roost-site temperature and recording the subsequent T
b changes in wintering blue tits (Cyanistes caeruleus L.), assuming that blue tits would respond to treatment by increasing T
b. We found that birds increased T
b when roost-site temperature was increased, but only at low ambient temperatures. Moreover, birds with larger fat reserves
regulated T
b at higher levels than birds carrying less fat. This result implies that a roosting blue tit maintains its T
b at the highest affordable level, as determined by the interacting effect of ecophysiological costs associated with rest-phase
hypothermia and energy reserves, in order to minimize potential fitness costs associated with a low T
b. 相似文献
15.
Extreme environmental conditions present challenges for thermoregulation in homoeothermic organisms such as mammals. Such challenges are exacerbated when two stressors are experienced simultaneously and each stimulus evokes opposing physiological responses. This is the case of cold, which induces an increase in thermogenesis, and hypoxia, which suppresses metabolism conserving oxygen and preventing hypoxaemia. As an initial approach to understanding the thermoregulatory responses to cold and hypoxia in a small mammal, we explored the effects of acclimation to these two stressors on the body temperature (Tb) and the daily and ultradian Tb variations of Sprague-Dawley rats. As Tb is influenced by sleep-wake cycles, these Tb variations reflect underlying adjustments in set-point and thermosensitivity. The Tb of rats decreased precipitously during initial hypoxic exposure which was more pronounced in cold (Tb=33.4±0.13) than in room temperature (Tb=35.74±0.17) conditions. This decline was followed by an increase in Tb stabilising at a new level ~0.5 °C and ~1.4 °C below normoxic values at room and cold temperatures, respectively. Daily Tb variations were blunted during hypoxia with a greater effect in the cold. Ultradian Tb variations exhibited daily rhythmicity that disappeared under hypoxia, independent of ambient temperature. The adjustments in Tb during hypoxia and/or cold are in agreement with the hypothesis that an initial decrease in the Tb set-point is followed by its partial re-establishment with chronic hypoxia. This rebound of the Tb set-point might reflect cellular adjustments that would allow animals to better deal with low oxygen conditions, diminishing the drive for a lower Tb set-point. Cold and hypoxia are characteristic of high altitude environments. Understanding how mammals cope with changes in oxygen and temperature will shed light into their ability to colonize new environments along altitudinal clines and increase our understanding of how Tb is regulated under stimuli that impose contrasting physiological constraints. 相似文献
16.
Alex Agostini Silvia Pignata Roberta Camporeale Kathryn Scott Jillian Dorrian Anne Way 《Chronobiology international》2018,35(5):691-704
Studies suggest that there may be an association between sleep and growth; however, the relationship is not well understood. Changes in biology and external factors such as school schedule heavily impact the sleep of adolescents, during a critical phase for growth. This study assessed the changes in sleep across school days, weekends and school holidays, while also measuring height and weight changes, and self-reported alterations in food intake and physical activity. The impact of morningness–eveningness (M-E) on height change and weight gain was also investigated. In a sample of 63 adolescents (mean age = 13.13, SD = 0.33, 31 males) from two independent schools in South Australia, height and weight were measured weekly for 4 weeks prior to the school holidays and 4 weeks after the school holidays. Participants also completed a Morningness/Eveningness Scale and 7-day sleep, diet and physical activity diaries prior to, during and after the school holidays. Participants at one school had earlier wake times during the weekends than participants attending the other school, leading to a significantly shorter sleep duration on weekends for those participants. Regardless of school, sleep was significantly later and longer during the holidays (p < 0.001) and those with a stronger morning preference fell asleep (F18,36 = 3.4, p = 0.001) and woke (F18,44 = 2.0, p = 0.027) earlier than evening types. Growth rate was lower during the holiday weeks. For those attending the school with limited sleep in opportunities, growth after the holidays was lower for those with greater evening preference, whereas for those at the other school, growth was greater for those with greater evening preference. The increase in average weight from pre- to post-holidays was greater for those attending the school with limited opportunities to sleep longer. Participants reported greater food intake during the holidays compared to school days and greater physical activity levels on weekends compared to school days, and school days compared to holidays. Results suggest that time of day preference may impact growth, with evening types who cannot sleep in growing at a slower rate than evening types who can or morning types. This may be related to sleep restriction. Despite sleep being both later and longer during the school holidays, participants’ growth slowed during the holiday period. It is possible that this may be a reflection of other behavioural changes in the holidays (increased food intake and reduced physical activity), as sleep timing during the school period was related to growth. 相似文献
17.
Thermoregulation in free‐ranging ground woodpeckers Geocolaptes olivaceus: no evidence of torpor
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Heterothermic responses characterised by pronounced hypometabolism and reductions in body temperature (Tb) are one of the most effective ways in which small endotherms can offset the energetic cost of endothermic homeothermy. It remains unclear, therefore, why daily torpor and hibernation are restricted to only a subset of avian lineages. To further our understanding of the phylogenetic distribution of avian torpor, we investigated winter thermoregulation in the southern African ground woodpecker Geocolaptes olivaceus. We considered this species a good candidate for heterothermy, because it is resident year‐round in mountainous regions with cold winters and reliant on small ectothermic prey. We recorded Tb patterns in free‐ranging individuals and measured Tb and metabolic rates in captive individuals. Neither free‐ranging nor captive woodpeckers showed any indication of daily torpor or even shallow rest‐phase hypothermia. All birds maintained bimodally distributed Tb characteristic of classic endothemic homeothermy, with a mean rest‐phase Tb of 37.9 ± 0.2°C and no data below 37.0°C. The mean circadian amplitude of Tb was 4.2°C, equivalent to approximately twice the expected value. There was some evidence of seasonal acclimatisation in Tb, with a small decrease in rest‐phase Tb with the onset of the austral winter. Captive birds showed patterns of resting metabolic rate and Tb consistent with the classic model of endothermic homeothermy. The apparent absence of torpor in G. olivaceus supports the notion that, unlike the case in mammals, many avian taxa that may a priori be expected to benefit from deep heterothermy do not use it. 相似文献
18.
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
19.
Susan Kohl Malone Babette Zemel Charlene Compher Margaret Souders Jesse Chittams Aleda Leis Thompson 《Chronobiology international》2016,33(9):1255-1266
The relationship between sleep duration and obesity in adolescents is inconclusive. This may stem from a more complex relationship between sleep and obesity than previously considered. Shifts toward evening preferences, later sleep–wake times and irregular sleep–wake patterns are typical during adolescence but their relationship to body mass index (BMI) has been relatively unexplored. This cross-sectional study examined associations between sleep duration, midpoint of sleep and social jet lag (estimated from 7 days of continuous actigraphy monitoring), and morningness/eveningness with BMIs (BMI z-scores) and waist-to-height ratios in 14–17-year-old adolescents. Seventy participants were recruited from ninth and tenth grades at a public high school. Participants’ characteristics were as follows: 74% female, 75% post-pubertal, 36% Hispanic, 38% White, 22% Black, 4% Asian and 64% free/reduced lunch participants with a mean age of 15.5 (SD, 0.7). Forty-one percent of the participants were obese (BMI ≥ 95th percentile); 54% were abdominally obese (waist-to-height ratio ≥ 0.5). Multivariable general linear models were used to estimate the association between the independent variables (school night sleep duration, free night sleep duration, midpoint of sleep (corrected), social jet lag and morningness/eveningness) and the dependent variables (BMI z-scores and waist-to-height ratios). Social jet lag is positively associated with BMI z-scores (p < 0.01) and waist-to-height ratios (p = 0.01). Midpoint of sleep (corrected) is positively associated with waist-to-height ratios (p = 0.01). After adjusting for social jet lag, school night sleep duration was not associated with waist-to-height ratios or BMI z-scores. Morningness/eveningness did not moderate the association between sleep duration and BMI z-scores. Findings from this study suggest that chronobiological approaches to preventing and treating obesity may be important for accelerating progress in reducing obesity rates in adolescents. 相似文献
20.
《Chronobiology international》2013,30(2):121-126
Thyroxine (T4) and triiodothyronine (T3) plasma concentrations have been determined during 24-hr sampling periods in six mongrels (age 12-36 months), six beagles (age 35-37 months), three labradors (age 3.5 months) and three beagles (age 5 months). The mean T4 levels of the labradors were significantly lower than the values found for mongrels or older beagles (P < 0.05), whereas T3 was higher in the 5 month old beagles compared to the mongrels (P < 0.001), young beagles (P < 0.05) or labradors (P < 0.01).Circadian and ultradian rhythmicities have been evaluated by cosinor and Fourier analysis. Mongrels and older beagles did have a 12-hr rhythmicity in plasma T4 (P < 0.05), whereas 5 month old beagles had a circadian one (P < 0.01). A 12-hr rhythmicity was also found for T3 in the older Beagles (P < 0.05). However, Fourier analysis indicated that the daily variation in T4 and T3 plasma levels was inadequately mathematically described by single sinusoidal rhythm and that more harmonic components are to be taken into account.The obtained data during a 24-hr period indicate that T4 and T3 concentrations in plasma may vary according to breed, age and sampling hour. 相似文献