Daily Rhythms of Metabolic Rate and Body Temperature of Two Murids from Extremely Different Habitats

Daily circadian rhythms of body temperature (T_b) and oxygen consumption (VO₂) were measured in two murid species, which occupy extremely different habitats in Israel. The golden spiny mouse (Acomys mssalus) is a diurnal murid distributed in arid and hot parts of the great Syrio-African Rift Valley, while the broad-toothed field mouse (Apodeinns mystacinus) is a nocturnal species that inhabits the Mediterranean woodlands. In both species, the daily rhythms of T_b and VO₂ are entrained by the photoperiod. Under laboratory experimental conditions (ambient temperature T_a = 33^oC and photoperiod regime of 12L: 12D), Acomys russatus exhibits a tendency towards a nocturnal activity pattern, compared to the diurnal activity displayed by this species under natural conditions. Under the same photoperiod regime and at T_a = 28^oC, Apodemus mystacinus displays nocturnal activity, as observed under natural conditions. The maximal values of T_b were recorded in Acomys russatus at midnight (23:50 h), while the maximal values of VO₂ were recorded at the beginning of the dark period (18:20 h). In Apodemus mystacinus, the maximal values of T_b and VO₂ were recorded at 23:40 and 20:00 h, respectively. The ecophysiological significance of these results is discussed further.     

Light Synchronization of the Daily Spawning Rhythms of Gilthead Sea bream (Sparus aurata L) Kept under Different Photoperiod and after Shifting the LD Cycle

Reproduction in most fish is typically a seasonal process, as spawning takes place usually at a given time of the year, depending on the reproduction strategy of the species, to ensure maximal survival of offspring. Nevertheless, fish reproduction cannot be considered an exclusively annual phenomenon, because spawning may also show daily rhythmicity. In this study, we investigated the existence of a daily spawning rhythm in gilthead seabream (Sparus aurata L) exposed to different light‐dark (LD) cycles and at different times of the year using an automatic and programmable egg collector. Floatability and fertilization rates were analyzed at different times throughout the 24 h. The results showed a daily spawning rhythm with spanning occurring from 14:30 to 21:30 h, with the acrophase (peak time) being 18:29 and 18:08 h in fish exposed to an artificial photoperiod of 9L∶15D in winter and in spring, respectively. Nevertheless, in fish exposed to a natural photoperiod of 12L∶12D in spring, the acrophase of the rhythm was recorded later, at 21:28 h. The average fertilization rate was 87%, and no significant differences were found between the different hours of spawning. Moreover, when the LD cycle (9L∶15D) was shifted by 12 h, the daily spawning rhythm gradually re‐synchronized, resuming a stable phase‐relationship after 4–5 transient days, which is characteristic of a endogenous circadian rhythm. Our results clearly demonstrated the existence of a 24 h period of spawning in gilthead sea bream, with a peak anticipating the forthcoming night, and its capacity to gradually re‐synchronize after a 12 h shift in the LD cycle, pointing to the endogenous nature of this rhythm. These findings will be valuable for better understanding the reproductive physiology of this species and for optimizing the protocols of egg collection and larvae production in aquaculture. (Author correspondence: javisan@um.es)     

Differences in Daily Rhythms of Wrist Temperature Between Obese and Normal-Weight Women: Associations With Metabolic Syndrome Features

The circadian rhythm of core body temperature is associated with widespread physiological effects. However, studies with other more practical temperature measures, such as wrist (WT) and proximal temperatures, are still scarce. The aim of this study was to investigate whether obesity is associated with differences in mean WT values or in its daily rhythmicity patterns. Daily patterns of cortisol, melatonin, and different metabolic syndrome (MetS) features were also analyzed in an attempt to clarify the potential association between chronodisruption and MetS. The study was conducted on 20 normal-weight women (age: 38?±?11 yrs and BMI: 22?±?2.6?kg/m²) and 50 obese women (age: 42?±?10 yrs and BMI: 33.5?±?3.2?kg/m²) (mean?±?SEM). Skin temperature was measured over a 3-day period every 10?min with the “Thermochron iButton.” Rhythmic parameters were obtained using an integrated package for time-series analysis, “Circadianware.” Obese women displayed significantly lower mean WT (34.1°C?±?0.3°C) with a more flattened 24-h pattern, a lower-quality rhythm, and a higher intraday variability (IV). Particularly interesting were the marked differences between obese and normal-weight women in the secondary WT peak in the postprandial period (second-harmonic power [P2]), considered as a marker of chronodisruption and of metabolic alterations. WT rhythmicity characteristics were related to MetS features, obesity-related proteins, and circadian markers, such as melatonin. In summary, obese women displayed a lower-quality WT daily rhythm with a more flattened pattern (particularly in the postprandial period) and increased IV, which suggests a greater fragmentation of the rest/activity rhythm compared to normal-weight women. These 24-h changes were associated with higher MetS risk. (Author correspondence: garaulet@um.es)     

Daily rhythm of oxygen consumption and thermoregulatory responses in some European winter- or summer-acclimatized finches at different ambient temperatures

The oxygen consumption of European finches, the siskin (Carduelis spinus), the brambling (Fringilla montifringilla), the bullfinch (Pyrhulla pyrhulla), the greenfinch (Carduelis chloris) and the hawfinch (Coccothraustes coccothraustes), was recorded continuously while ambient temperature was decreased stepwise from +30 down to-75°C. The oxygen consumption, body temperature (telemetrically), and shivering (integrated pectoral electromyography) of greenfinches were measured simultaneously at ambient temperatures between +30 and-75°C. Maximum heat production, cold limit, lower critical temperature, basal metabolic rate and thermal conductance (of the greenfinch) were determined. The diurnal variation of oxygen consumption of siskins and greenfinches was recorded at thermoneutrality and below the thermoneutral zone in winter- and summer-acclimatized birds. The diurnal variation of body temperature and thermal conductance of greenfinches were also determined. The diurnal variation of heat production was not seasonal or temperature dependent in the siskin and in the greenfinch. Nocturnal reduction of oxygen consumption saved 15–33% energy in the siskin and greenfinch. Body temperature of the greenfinch was lowered by 2.5–3.4°C. The nocturnal reduction of thermal conductance in the greenfinch was 39–48%. The basal metabolic rate was lowest in the largest bird (hawfinch) and highest in the smallest bird (siskin). The values were in the expected range. The heat production capacity of finches in winter was 4.7 times basal metabolic rate in the siskin, 4.2 times in the brambling, 3.5 times in the greenfinch and 2.9 times in the bullfinch and hawfinch. The heat production capacity of the siskin and greenfinch was not significantly lower in summer. The cold limit temperatures (°C) in winter were-61.2 in the siskin,-41.3 in the greenfinch,-37.0 in the bullfinch,-35.7 in the brambling and-28.9 in the hawfinch. The cold limit was 14.3°C higher in summer than in winter in the siskin and 8.7°C in the greenfinch. Thermal insulation of the greenfinch was significantly better in winter than in summer. The shivering of the greenfinch increased linearly when ambient temperature was decreased down to-40°C. Maintenance of shivering was coincident with season. In severe cold integrated pectoral electromyography did not correlate with oxygen consumption as expected. The possible existence of non-shivering thermogenesis in birds is discussed. It is concluded that the acclimatization of European finches is primarily metabolic and only secondly affected by insulation.Abbreviations AAT avian adipose tissue - bm body mass - BMR basal metabolic rate - C _t thermal conductance - EMG electromyogram - HP heat production - HP _max maximum heat production - MR metabolic rate - NST non-shivering thermogenesis - RMR resting metabolic rate - RQ respiratory quotient - T _a ambient temperature - T _b body temperature - T _c colonic temperature - T _1c lower critical temperature - TNZ thermoneutral zone - T _st shivering threshold temperature - V oxygen consumption     

中缅树鼩体温、代谢率和蒸发失水日节律

为研究中缅树鼩(Tupaia belangeri)体温、代谢率和蒸发失水的日节律变化,采用植入式体温计测定了中缅树鼩24 h的体温,以及24 h中4个时间段(05:00～07:00时、11:00～13:00时、17:00～19:00时和23:00～01:00时)热中性区(30℃)的静止代谢率(RMR)、非颤抖性产热(NST)和蒸发失水(EWL)。结果显示,中缅树鼩的体温具有日节律变化,最高值和最低值分别出现在11:00时和03:00时,各为(39.45±0.26)℃和(36.34±0.24)℃;静止代谢率、非颤抖性产热和蒸发失水在4个时间段都有显著差异,表现出显著的日节律变化,代谢率在23:00～01:00时最大,O2含量为(2.58±0.04)ml/(g.h),在11:00～13:00时最小,O2含量为(2.28±0.09)ml/(g.h);非颤抖性产热在05:00～07:00时最大,O2含量为(3.08±0.14)ml/(g.h),在11:00～13:00最小,O2含量为(2.69±0.63)ml/(g.h);蒸发失水在17:00～19:00时最大,失水量为(3.60±0.31)mg/(g.h)。结果表明,体温的日节律变化主要与环境温度的日节律变化和下午出窝取食活动性增强有关;当夜晚环境温度相对较低的时候,通过增强静止代谢率和非颤抖性产热来增加产热,而白天环境温度相对较高的时候,通过增强蒸发失水散热来调节体温。     

大绒鼠及高山姬鼠体温调节和蒸发失水的日节律

为比较横断山区同域分布物种大绒鼠(Eothenomys miletus)和高山姬鼠(Apodemus chevrieri)的日节律特征,对两种鼠在24 h中4个时间段(04:00～06:00时、10:00～12:00时、16:00～18:00时和22:00～24:00时)的体温和蒸发失水进行了测定.结果显示,大绒鼠、高...     

Role of SCN in Daily Rhythms of Plasma Glucose,FFA, Insulin and Glucagon

The daily changes in plasma glucose, FFA, insulin and glucagon concentrations in rats under 12 hr-12 hr light-dark conditions, and the role of the suprachiasmatic nucleus (SCN) of the hypothalamus in these changes were examined. In sham-operated rats, the four parameters showed significant daily rhythms. However, after bilateral lesions of the SCN, daily rhythms could not be detected in these parameters under the present experimental conditions. Furthermore, after the SCN lesions the plasma glucose concentration remained at the minimum level of that in sham-operated rats, while the plasma insulin and glucagon concentrations reduced to approximately the mean level and about half the minimum level of sham-operated rats, respectively, and the FFA concentration lowered to somewhat below the minimum level. Gradual increase in the plasma insulin concentration at the end of the light period was observed in intact rats even after starvation for 24 hr. These findings suggest that the SCN is essential for generation of the daily changes in the plasma glucose, FFA, insulin and glucagon concentrations and also that it plays critical roles in regulation of the secretion of pancreatic hormones. The gradual increase in the plasma insulin level observed at the end of the light period is discussed in connection with initiation of spontaneous feeding behaviour.     

棕眉山岩鹨的代谢产热特征的初步研究

实验采用封闭式流体压力呼吸计和数字式温度计 ,分别测定了环境温度 (Ta)在 5～ 35℃范围内棕眉山岩鹨 (Prunellamontanella)的耗氧量和体温 (Tb) ,由此计算出代谢率 (MR)、热传导率 (C)和代谢预期比与热传导预期比 (F)等值 ,以探讨该种的代谢产热特征。结果表明 :棕眉山岩鹨在Ta 为 5～ 35℃时 ,Tb 基本维持恒定 (为 4 1 2 5± 0 12℃ ) ,MR的最低值为 4 2 7± 0 0 7mLO2 /(g·h) ;Ta 在 5～ 2 4℃时 ,MR与之负相关 :MR [mLO2 /(g·h) ]=10 39- 0 2 4Ta℃ ;Ta 在 5～ 2 6 5℃时 ,C最低且基本保持恒定 ,平均为 0 2 6±0 0 0mLO2 /(g·h·℃ ) ;Ta 在 2 4～ 30℃时 ,F值为 1 0 5 ,表明该种具有较好的体温调节能力。与热带地区鸟类比较 ,棕眉山岩鹨具较高的MR和Tb,稍高的C ,符合北方小型鸟类的代谢特点 ,能较好的适应冬寒冷、夏炎热的环境。     

Thermoregulatory behaviour in two species of iguanid lizards (Crotaphytus collaris andSauromalus obesus): diel variation and the effect of pinealectomy

Summary Thermal selection by collared lizards (Crotaphytus collaris) and chuckawallas (Sauromalus obesus) was studied in continuously operating laboratory thermal gradients in a 12L12D photoperiod in spring-summer. In both species, selected temperatures above the median were higher during the day than at night. Below the median selected temperature, however, nighttime temperature significantly exceeded daytime temperature in chuckawallas but not in collared lizards. Pinealectomized collared lizards selected significantly lower temperatures than sham-operated or intact controls. This effect was most pronounced at night. Pinealectomy had no effect on the temperatures selected by chuckawallas. The significance of these results is discussed in relation to the seasonal life-history strategy of these two species.     

Entrainment to Light of Circadian Activity Rhythms in Tench (Tinca tinca)

The present article analyzes locomotor activity rhythms in Tinca tinca. To that end, three different experiments were conducted on 24 animals (20 g body weight) kept in pairs in 60‐liter aquaria fitted with infrared sensors connected to a computer to continuously record fish movements. The first experiment was designed to study the endogenous circadian clock under free‐running conditions [ultradian 40:40 min LD pulses and constant dark (DD)] and after shifting the LD cycle. Our results demonstrate that tench has a strictly nocturnal activity pattern, an endogenous rhythm being evident in 45.8% of the fish analyzed. The second experiment was conducted to test the influence of different photoperiods (LD 6:18, 12:12, 18:6, and 22:2) on locomotor activity, the results showing that even under an extremely long photoperiod, tench activity is restricted to dark hours. The third experiment examined the effect of light intensity on locomotor activity rhythms. When fish were exposed to decreasing light intensities (from 300:0 lux to 30:0, 3:0, and 0.3:0 lux) while maintaining a constant photoperiod (LD 12:12), the highest percentage of locomotor activity was in all cases associated with the hours of complete darkness (0 lux). In short, our results clearly show that (a) tench is a species with a strictly nocturnal behavior, and (b) daily activity rhythms gradually entrain after shifting the LD cycle and persist under free‐running conditions, pointing to their circadian nature. However, light strongly influences activity rhythms, since (c) the length of the active phase is directly controlled by the photophase, and (d) strictly nocturnal behavior persists even under very dim light conditions (0.3 lux). The above findings deepen our knowledge of tench behavior, which may help to optimize the aquacultural management of this species, for example, by adjusting feeding strategies to their nocturnal behavior.     

Field Chronobiology of a Molluscan Bivalve: How the Moon and Sun Cycles Interact to Drive Oyster Activity Rhythms

The present study reports new insights into the complexity of environmental drivers in aquatic animals. The focus of this study was to determine the main forces that drive mollusc bivalve behavior in situ. To answer this question, the authors continuously studied the valve movements of permanently immersed oysters, Crassostrea gigas, during a 1-year-long in situ study. Valve behavior was monitored with a specially build valvometer, which allows continuously recording of up to 16 bivalves at high frequency (10?Hz). The results highlight a strong relationship between the rhythms of valve behavior and the complex association of the sun-earth-moon orbital positions. Permanently immersed C. gigas follows a robust and strong behavior primarily driven by the tidal cycle. The intensity of this tidal driving force is modulated by the neap-spring tides (i.e., synodic moon cycle), which themselves depend of the earth–moon distance (i.e., anomalistic moon cycle). Light is a significant driver of the oysters' biological rhythm, although its power is limited by the tides, which remain the predominant driver. More globally, depending where in the world the bivalves reside, the results suggest their biological rhythms should vary according to the relative importance of the solar cycle and different lunar cycles associated with tide generation. These results highlight the high plasticity of these oysters to adapt to their changing environment. (Author correspondence: d.tran@epoc.u-bordeaux1.fr)     

The Daily Rhythms in the Core Temperature during Spring and Autumn under Natural Conditions in Young Women

Studies of the daily rectal temperature rhythms during May and October–November in three female subjects leading normal lives under natural conditions disclosed that although a rhythm of rectal temperature existed in all three subjects in both seasons, the temperature level seems to be lower in October–November than in May, especially during the nighttime. The phasing of the rectal temperature rhythm did not seem to differ between the two seasons.     

Daily rhythms of nonshivering thermogenesis in common spiny mice Acomys cahirinus under short and long photoperiods

Daily rhythms of nonshivering thermogenesis NST were studied in common spiny mice Acomys cahirinus, acclimated to different photoperiod regimes (16L:8D and 8L:16D) at a constant ambient temperature of 26°C. Noradrenaline NA (1.5 mg/kg subcutaneous) was injected at: 06:00, 12:00, 18:00 and 24:00 h (±15 min). NST was measured as the ratio between the maximal oxygen consumption (VO₂) as response to NA — VO₂NA and VO₂ measured at 26°C — VO_{2 min}. Rectal temperatures T_bNA and T_{b min} respectively were recorded at the end of VO₂ measurements. Significant variations in T_{b min}, T_bNA, and NST were revealed, under the two different photoperiod regimes. Significant differences in VO_{2 min}, NST, T_{b min} and T_bNA were also recorded within each photoperiod acclimation group. These results suggest that daily and photoperiod depended variations in the brown adipose tissue activity, presumably emerge from amount of unoccupied receptors or changes in the receptors affinity to NA.     

Body temperature variation of free-ranging and captive southern brown bandicoots Isoodon obesulus (Marsupialia: Peramelidae)

To investigate patterns of thermoregulation in free-ranging and captive southern brown bandicoots Isoodon obesulus, we measured abdominal body temperature (T_b) of five free-ranging bandicoots over 42 days using implanted data loggers and T_b of three captive bandicoots over 3 months using implanted temperature-sensitive radio transmitters. Bandicoots in the wild had a mean T_b of 36.5±1.0 °C (range 33.4–39.8 °C) and showed a pronounced nychthemeral pattern with two distinct temperature phases. T_b increased at 13:30±2.6 h each day and remained high for 10.65±2.07 h, suggesting a crepuscular and early evening activity pattern. Daily T_b variation of I. obesulus would save considerable energy by reducing daytime thermoregulatory costs in the wild. Captive bandicoots had a similar mean body temperature (36.9±0.2°C) and range (33.0–39.9°C) as free-ranging bandicoots. However, the nychthemeral T_b pattern of captive bandicoots was different from free-ranging bandicoots, with a less pronounced daily cycle and the nocturnal rise in T_b occurring mainly at sunset and the daily decline occurring mainly at dawn.     

松鼠秋冬季节日活动节律的初步研究

观察了小兴安岭林区秋冬季节松鼠日活动节律。松鼠秋季的日活动节律为双峰型 ,冬季的日活动节律为单峰型 ,秋季日活动时间为 (9 1 0± 1 0 3 )h ,其中取食时间所占的比率为 85 5 0 % ,冬季日活动时间为 (4 62± 0 5 1 )h,取食时间所占的比率为 88 2 5 % ,两季节间的日活动时间存在显著的季节差异(t=8 1 7,P <0 0 5 )。松鼠日活动节律和活动时数受日照时数、温度、食物和人为干扰等因素的影响     

Daily Rhythms of Core Temperature and Locomotor Activity Indicate Different Adaptive Strategies to Cold Exposure in Adult and Aged Mouse Lemurs Acclimated to a Summer-Like Photoperiod

Daily variations in core temperature (Tc) within the normothermic range imply thermoregulatory processes that are essential for optimal function and survival. Higher susceptibility towards cold exposure in older animals suggests that these processes are disturbed with age. In the mouse lemur, a long-day breeder, we tested whether aging affected circadian rhythmicity of Tc, locomotor activity (LA), and energy balance under long-day conditions when exposed to cold. Adult (N?=?7) and aged (N?=?5) mouse lemurs acclimated to LD14/10 were exposed to 10–day periods at 25 and 12°C. Tc and LA rhythms were recorded by telemetry, and caloric intake (CI), body mass changes, and plasma IGF-1 were measured. During exposure to 25°C, both adult and aged mouse lemurs exhibited strong daily variations in Tc. Aged animals exhibited lower levels of nocturnal LA and nocturnal and diurnal Tc levels in comparison to adults. Body mass and IGF-1 levels remained unchanged with aging. Under cold exposure, torpor bout occurrence was never observed whatever the age category. Adult and aged mouse lemurs maintained their Tc in the normothermic range and a positive energy balance. All animals exhibited increase in CI and decrease in IGF-1 in response to cold. The decrease in IGF-1 was delayed in aged mouse lemurs compared to adults. Moreover, both adult and aged animals responded to cold exposure by increasing their diurnal LA compared to those under Ta?=?25°C. However, aged animals exhibited a strong decrease in nocturnal LA and Tc, whereas cold effects were only slight in adults. The temporal organization and amplitude of the daily phase of low Tc were particularly well preserved under cold exposure in both age groups. Sexually active mouse lemurs exposed to cold thus seemed to prevent torpor exhibition and temporal disorganization of daily rhythms of Tc, even during aging. However, although energy balance was not impaired with age in mouse lemurs after cold exposure, aging was associated with lower LA and Tc during the night and delayed decrease in IGF-1. This might reflect that adaptive strategies to cold exposure differ with age in mouse lemurs acclimated to a summer-like photoperiod.     

Gene or Size: Metabolic Rate and Body Temperature in Obese Growth Hormone‐Deficient Dwarf Mice

Objective: SMA1 mice carry a missense mutation in the growth hormone gene that leads to semidominant dwarfism and obesity. In this study, the basic thermal and metabolic properties of SMA1 mice were examined to detect metabolic alterations that can support the accretion of excess fat. Research Methods and Procedures: Basal and resting metabolic rates (RMRs) in wild‐type and SMA1 (sma1/+ and sma1/sma1) mice were determined by indirect calorimetry. Body temperature (T_b) was recorded using intraperitoneally implanted temperature‐sensitive transmitters, and body composition was determined by DXA. Results: SMA1 mice have proportionally lower basal and resting metabolic rates, higher body mass (BM)‐specific RMRs, and a higher lower critical temperature, and display a decrease in T_b by 0.4 °C in sma1/+ and 0.9 °C in sma1/sma1. Discussion: The analysis of gene effects on BM and energy expenditure in mouse mutants must consider the appropriate allometric relationship between BM and metabolic rate. With the exception of T_b, all metabolic alterations observed in SMA1 reflect reduced size.     

Chronic Administration of Imipramine and Lithium Changes the Phase-Angle Relationship Between the Activity and Core Body Temperature Circadian Rhythms in Rats

Evidence suggests that there is an association between the pathophysiology of depression and a disturbance of circadian rhythms. Accordingly, attention has focused on the possible effects of antidepressants on circadian rhythms. In the present study, we examined the effects of chronic administration of two clinically effective antidepressant agents, imipramine and lithium, on several circadian rhythms in the rat. Activity, core body temperature, and drinking rhythms were assessed in constant darkness (DD) and light-dark (LD) conditions. In DD, lithium significantly lengthened the circadian period of the activity, temperature, and drinking rhythms, while imipramine had no effect. In LD, both drugs significantly delayed the phase of the activity rhythm, but did not change that of the other two rhythms. As a result, the phase-angle differences between the activity and temperature rhythms significantly increased. Neither lithium nor imipramine produced any effect on the resynchronization of these rhythms after an 8-h delay in the LD cycle. These results indicate that although both drugs produced different effects on the circadian period of individual rhythms, both caused a relative phase advance of the temperature rhythm as compared to the activity rhythm, and this effect may be related to the similarity in their antidepressant effects. (Chronobiology International, 13(4), 251-259, 1996)     

Altered Orcadian Rhythms of Blood Pressure and Heart Rate in Non-Hemodialysis Chronic Renal Failure

The extended use of ambulatory monitoring has permitted the identification of many conditions in which the circadian rhythm of blood pressure is altered. The common denominator seems to be an impairment of the autonomic nervous system function. We examined whether the circadian blood pressure rhythm is altered in chronic renal failure (where autonomic dysfunction is usually present) by using a standardized chronobiological inferential statistical method in hospitalized subjects. For this purpose, a group of 30 non-hemodialysis hypertensive patients with chronic renal failure was compared with a second group of 30 patients affected by uncomplicated mild-to-moderate essential hypertension. The two groups were matched by age, sex and circadian mesors of blood pressure. Diet, meal times, sleep and activity logs were standardized. Blood pressure and heart rate recordings were obtained by using an automatic oscillometric recorder and subsequently analyzed according to the cosinor method. A mean circadian rhythm of blood pressure was documented in both groups, but while the mean acrophases occurred between 2 and 3 p.m. in essential hypertension, in renal failure they were between 11 p.m. and midnight for blood pressure and around 7 p.m. for heart rate. In addition, the mean circadian amplitudes were significantly lower in renal failure, while the mean circadian mesor of heart rate was significantly higher. Our data demonstrate that the circadian rhythms of blood pressure and heart rate are altered also in hypertension due to chronic renal failure.