Diurnal Activity Rhythm Research Articles

Sleep-wake regulation is altered in leptin-resistant (db/db) genetically obese and diabetic mice

Recent epidemiological and clinical studies indicate that the control of sleep-wake states may be an important factor in the regulation of energy metabolism. Leptin is a peripherally synthesized hormone that has critical signaling properties in the brain for the control of long-term energy homeostasis. In this study, we examined the hypothesis that leptin signaling exerts a role in sleep-wake regulation and that leptin may represent an important mechanistic link in the coordination of sleep-wake states and metabolism. Sleep-wake patterns were recorded in a genetic mouse model of obesity and diabetes, the db/db mouse, which harbors a mutation in a particular isoform of the leptin receptor (long form, LRb). We found that db/db mice exhibit a variety of alterations in sleep regulation, including an increase in overall sleep time, a dramatic increase in sleep fragmentation, attenuated diurnal rhythmicity in rapid eye movement sleep and non-rapid eye movement EEG delta power (a measure of sleep homeostatic drive), and a decrease in the compensatory response to acute (i.e., 6 h) sleep deprivation. The db/db mice also generated low amounts of locomotor activity and a reduction in the diurnal rhythm of activity. These results indicate that impaired leptin signaling has deleterious effects on the regulation of sleep amount, sleep architecture, and temporal consolidation of these arousal states. In summary, leptin may represent an important molecular component in the integration of sleep, circadian rhythms, and energy metabolism.

Retinal pathways influence temporal niche

In mammals, light input from the retina entrains central circadian oscillators located in the suprachiasmatic nuclei (SCN). The phase of circadian activity rhythms with respect to the external light:dark cycle is reversed in diurnal and nocturnal species, although the phase of SCN rhythms relative to the light cycle remains unchanged. Neural mechanisms downstream from the SCN are therefore believed to determine diurnality or nocturnality. Here, we report a switch from nocturnal to diurnal entrainment of circadian activity rhythms in double-knockout mice lacking the inner-retinal photopigment melanopsin (OPN4) and RPE65, a key protein used in retinal chromophore recycling. These mice retained only a small amount of rod function. The change in entrainment phase of Rpe65(-/-);Opn4(-/-) mice was accompanied by a reversal of the rhythm of clock gene expression in the SCN and a reversal in acute masking effects of both light and darkness on activity, suggesting that the nocturnal to diurnal switch is due to a change in the neural response to light upstream from the SCN. A switch from nocturnal to diurnal activity rhythms was also found in wild-type mice transferred from standard intensity light:dark cycles to light:dark cycles in which the intensity of the light phase was reduced to scotopic levels. These results reveal a novel mechanism by which changes in retinal input can mediate acute temporal-niche switching.

Glucocorticoids and cyclic AMP selectively increase hepatic lipin-1 expression, and insulin acts antagonistically

Glucocorticoids (GCs) increase hepatic phosphatidate phosphatase (PAP1) activity. This is important in enhancing the liver's capacity for storing fatty acids as triacylglycerols (TAGs) that can be used subsequently for beta-oxidation or VLDL secretion. PAP1 catalyzes the conversion of phosphatidate to diacylglycerol, a key substrate for TAG and phospholipid biosynthesis. PAP1 enzymes in liver include lipin-1A and -1B (alternatively spliced isoforms) and two distinct gene products, lipin-2 and lipin-3. We determined the mechanisms by which the composite PAP1 activity is regulated using rat and mouse hepatocytes. Levels of lipin-1A and -1B mRNA were increased by dexamethasone (dex; a synthetic GC), and this resulted in increased lipin-1 synthesis, protein levels, and PAP1 activity. The stimulatory effect of dex on lipin-1 expression was enhanced by glucagon or cAMP and antagonized by insulin. Lipin-2 and lipin-3 mRNA were not increased by dex/cAMP, indicating that increased PAP1 activity is attributable specifically to enhanced lipin-1 expression. This work provides the first evidence for the differential regulation of lipin activities. Selective lipin-1 expression explains the GC and cAMP effects on increased hepatic PAP1 activity, which occurs in hepatic steatosis during starvation, diabetes, stress, and ethanol consumption.

Seasonal changes in the circadian rhythm of the total antioxidant activity of human saliva

Seasonal changes in the diurnal rhythm of the total saliva antioxidant activity were monitored using coulometric titration. One-hour shifts of the acrophase of this rhythm towards earlier hours in the spring and in the opposite direction in the autumn could be related to the practice of changing the clock to winter and summer time.

Light and shape: A contribution to demonstrate morphological differences in diurnal and nocturnal teleosts

Light intensity is an important environmental factor affecting the structure of fish assemblages during the day-night cycle. Light influences how organisms perceive their environment, modulating their intraspecific and interspecific relationships. The relationship between light intensity variations and biological cycles should be observed at the level of organismal morphology. In this study the relationship between activity rhythms, thus light intensity experienced by fish in the period of major activity and external morphology, have been investigated. The morphological traits of 97 selected fish species were compared in order to determine the existence of a common morphological plan in agreement with their diurnal or nocturnal activity rhythm. Species sorting was performed by maximizing the diversity of activity rhythm, habitat choice, ecology, and trophic habits within the same family, to assess the importance of the day-night cycle on species morphology in relation to other environmental features. The morphological characters selected for the geometric morphometric analysis were body profile and the position of mouth, eye, pelvic, pectoral, dorsal, and caudal fin. The present analysis allowed different consensus forms for nocturnal and for diurnal species to be identified. Two-block Partial Least Squares analysis was then performed for the purpose of modeling the covariation between the form and two important external variables (ecology and activity).

Serotonin in alcoholic violent offenders.

Finnish alcoholic, impulsive, habitually violent offenders have been found to have low brain serotonin (5-hydroxytryptamine; 5-HT) turnover which is associated with impaired impulse control, a history of suicide attempts, hypoglycaemic tendency after an oral glucose load and diurnal activity rhythm dysregulation or hyperactivity. Relatively high cerebrospinal fluid (CSF) free testosterone concentration is a further characteristic of the offenders with antisocial personality disorder. The impulsive offenders may represent a behaviourally extreme group of type 2 alcoholics as defined by Cloninger. A large cohort of 800 subjects, including alcoholic violent offenders, their relatives and male controls, has now been gathered from Finland with support from the National Institute on Alcohol Abuse and Alcoholism. About 200 subjects have provided CSF samples. Leukocytes from the whole cohort have been harvested and immortalized. Genes regulating 5-HT functions are now being systematically analysed from these samples. Thus far, polymorphisms of the tryptophan hydroxylase (TPH) and 5-HT2C receptor genes have been the most informative findings.

Diurnal activity patterns of farm mink (Mustela vison) subjected to different feeding routines

Diurnal patterns and time courses of activity and feed availability were investigated in three generations of farmed mink (2003–2005) subjected to three different feedings routines; normal farm feeding (close to average ad libitum), ad libitum, and restricted feeding. The mink were fed daily at h12:00 (in 2005 at 13:00 h) and their activity were observed by hourly direct scanning during 24 h. On November 13, 2003 the feeding was postponed from 12:00 to 15:00 h and the activity observed from 9:00 to 17:00 h. The diurnal rhythm but not the average 24 h activity level differed between the mink on different feeding schedules. The diurnal activity rhythm in both the farm fed and the ad libitum fed mink consisted of three activity peaks; one around sunrise, one prior to feeding time, and one around sunset. However, the restrictively fed mink decreased their activity in the morning when feed was not available and increased their activity up to expected feeding time at noon and again around sunset. When feeding was postponed, the restrictively fed mink increased their activity up to expected feeding time, whereas the ad libitum or farm fed mink did not. The results indicate that mink fed restrictively synchronize their daily activity rhythm to the expected time of feeding. In addition, a high feeding motivation appears to be a precondition for circadian anticipatory activity in mink whereas anticipatory activity of mink fed ad libitum or close to ad libitum may be provoked by stimuli from the actual feeding procedure.

Day–night expression patterns of clock genes in the human pineal gland

Rhythm generation within the mammalian circadian system is achieved by clock genes and their protein products. As an integral part of this system, the pineal gland serves the need to tune the body to the temporal environment by the rhythmic synthesis and release of melatonin. A number of human disorders and syndromes are associated with alterations in circadian rhythms of clock genes and their protein products and/or a dysfunction in melatonin synthesis. In the human, little is known about the molecular signature of time management. Pineal tissue from regular autopsies was allocated to asserted time-of-death groups (dawn, day, dusk, night), and analyzed by RT-PCR, immunoblotting, immunohistochemistry, and confocal laser scanning microscopy for expression of clock genes. Despite the observed diurnal rhythms in activity of the arylalkylamine N-acetyltransferase and in melatonin content, mRNA levels for the clock genes Period1, Cryptochrome1, Clock, and Bmal1, and also amounts of corresponding clock gene proteins showed no differences between time- of-death groups. In contrast, a time-of-day-dependent nucleocytoplasmic shuttling of clock gene proteins was detected. These data confirm the minor importance of a transcriptional regulation for dynamics in the human pineal gland, and offer a novel twist in the molecular competence of clock gene proteins.

Diurnal activity rhythms and time budgets of captive Qinling golden takin (Budorcas taxicolor bedfordi) in the Qinling Mountains, Shaanxi, China

In July 2006, the diurnal activity rhythms of 13 heads of captive Qinling golden takin were observed in Shaanxi Provincial Centre for the Breeding and Conservation of Rare Wildlife (SPCBCRW) at daylight (from 9:00 am to 4:00 pm in July). The behavioral ethnogram was identified through observation at the sampling site, with the behaviors of golden takin recorded at 5 min interval using instantaneous scannable sampling method. The results indicated that the resting of golden takin took an important part in the daylight activities. Meanwhile, drinking and urinating and defecating were 1.92 and 0.54 and 0.92 times per head per day. Ambient temperature had a strong effect on the diurnal activity rhythms of golden takin. The diurnal activity rhymes were affected by ages of the animals effectively, which was expressed through differentiation of the time budgets. Moreover, different individuals in the same population showed some non-synchronously activity rhythms.

Transcriptional coactivator PGC-1α integrates the mammalian clock and energy metabolism

The mammalian clock regulates major aspects of energy metabolism, including glucose and lipid homeostasis and mitochondrial oxidative metabolism. The biochemical basis for coordinated control of the circadian clock and diverse metabolic pathways is not well understood. Here we show that PGC-1alpha (Ppargc1a), a transcriptional coactivator that regulates energy metabolism, is rhythmically expressed in the liver and skeletal muscle of mice. PGC-1alpha stimulates the expression of clock genes, notably Bmal1 (Arntl) and Rev-erbalpha (Nr1d1), through coactivation of the ROR family of orphan nuclear receptors. Mice lacking PGC-1alpha show abnormal diurnal rhythms of activity, body temperature and metabolic rate. The disruption of physiological rhythms in these animals is correlated with aberrant expression of clock genes and those involved in energy metabolism. Analyses of PGC-1alpha-deficient fibroblasts and mice with liver-specific knockdown of PGC-1alpha indicate that it is required for cell-autonomous clock function. We have thus identified PGC-1alpha as a key component of the circadian oscillator that integrates the mammalian clock and energy metabolism.

Regulation of Hypocretin (Orexin) Expression in Embryonic Zebrafish

Hypocretins/orexins are neuropeptides involved in the regulation of sleep and energy balance in mammals. Conservation of gene sequence, hypothalamic localization of cell bodies, and projection patterns in adult zebrafish suggest that the architecture and function of the hypocretin system are conserved in fish. We report on the complete genomic structure of the zebrafish and Tetraodon hypocretin genes and the complete predicted hypocretin protein sequences from five teleosts. Using whole mount in situ hybridization, we have traced the development of hypocretin cells in zebrafish from onset of expression at 22 h post-fertilization through the first week of development. Promoter elements of similar size from zebrafish and Tetraodon were capable of driving efficient and specific expression of enhanced green fluorescent protein in developing zebrafish embryos, thus defining a minimal promoter region able to accurately mimic the native hypocretin pattern. This enhanced green fluorescent protein expression also revealed a complex pattern of projections within the hypothalamus, to the midbrain, and to the spinal cord. To further analyze the promoter, a series of deletion and substitution constructs were injected into embryos, and resulting promoter activity was monitored in the first week of development. A critical region of 250 base pairs was identified containing a core 13-base pair element essential for hypocretin expression.

Temporal pattern of feeding activity in the firebug Pyrrhocoris apterus and its relation to sex, wing dimorphism and physiological state of adults

Abstract The present study tested whether the pattern of feeding activity in the firebug Pyrrhocoris apterus (L.) is sex‐ and wing morph‐related, diurnal or nocturnal, as well as whether the feeding rhythm persists in constant darkness. Temporal patterns of feeding activity are analysed in macropterous and brachypterous adults reared under long‐day (LD 18 : 6 h) and short‐day (LD 12 : 12 h) photoperiods, and in adults transferred to constant darkness. In females, the total feeding activity is highest in long‐day reproductively active brachypters, intermediate in short‐day diapausing brachypters, and lowest in macropters; the differences among males are substantially smaller. Although the total feeding activity of macropterous males is higher than in macropterous females, no sex‐related differences are found in feeding activity of diapausing and reproductively active brachypters. The frequency of feeding exhibits sex‐related differences, with obviously higher values in males. Mean feeding periods of macropterous and reproductively active brachypterous males are shorter than in females of the same wing morph. Mean interfeeding periods are longest in macropters, intermediate in diapausing brachypters, and shortest in reproductively active brachypters, and always lower in males than in females. The study shows that the feeding activity of P. apterus adults is age‐, sex‐ and wing morph‐related, and exhibits a diurnal pattern, except in reproductively active brachypterous females. The latter do not express a clear diurnal rhythm of feeding, presumably because of interactions with cycles of egg development and oviposition. The persistence of diurnal rhythm of feeding activity in short‐day brachypterous females transferred to constant darkness indicates an endogeneity of this rhythm in P. apterus.

A ‘polarisation sun‐dial’ dictates the optimal time of day for dispersal by flying aquatic insects

Summary1. Daily changes in the flight activity of aquatic insects have been investigated in only a few water beetles and bugs. The diel flight periodicity of aquatic insects and the environmental factors governing it are poorly understood.2. We found that primary aquatic insects belonging to 99 taxa (78 Coleoptera, 21 Heteroptera) fly predominantly in mid‐morning, and/or around noon and/or at nightfall. There appears to be at least four different types of diurnal flight activity rhythm in aquatic insects, characterised by peak(s): (i) in mid‐morning; (ii) in the evening; (iii) both in mid‐morning and the evening; (iv) around noon and again in the evening. These activity maxima are quite general and cannot be explained exclusively by daily fluctuations of air temperature, humidity, wind speed and risks of predation, which are all somewhat stochastic.3. We found experimental evidence that the proportion (%) P(θ) of reflecting surfaces detectable polarotactically as ‘water’ is always maximal at the lowest (dawn and dusk) and highest (noon) angles of solar elevation (θ) for dark reflectors while P(θ) is maximal at dawn and dusk (low solar elevations) for bright reflectors under clear or partly cloudy skies.4. From the temporal coincidence between peaks in the diel flight activity of primary aquatic insects and the polarotactic detectability P(θ) of water surfaces we conclude that the optimal times of day for aquatic insects to disperse are the periods of low and high solar elevations θ. The θ‐dependent reflection–polarisation patterns, combined with an appropriate air temperature, clearly explain why polarotactic aquatic insects disperse to new habitats in mid‐morning, and/or around noon and/or at dusk. We call this phenomenon the ‘polarisation sun‐dial’ of dispersing aquatic insects.

Developmentally determined attenuation in circadian rhythms links chronobiology to social organization in bees

We investigated labor-related plasticity in the circadian clock of the bumblebee Bombus terrestris. Bumblebee workers vary enormously in body size, and we found that size, division of labor, and diurnal rhythms in activity are correlated in B. terrestris colonies. Large workers typically perform foraging activities with strong diurnal rhythms and low activity at night, whereas small bees typically care for (nurse) brood around the clock with weak or no diurnal rhythms. Under constant laboratory conditions, circadian rhythms in locomotor activity were weaker, less stable, and developed at a later age in small (nurse-size) bees compared to their larger (forager-size) sisters. Under a light:dark illumination regime, many small bees, particularly at a young age, were active during the dark phase, fewer small bees developed rhythms, and they did so later compared to large bees. Taken together these findings reveal naturally occurring attenuation or suppression in the circadian clock of small bees that is determined during pre-adult development. This deficiency in clock function, however, does not result in pathology but rather appears to be functionally significant, because it is associated with around-the-clock brood care activity and therefore apparently improves divisions of labor and colony efficiency. This in turn suggests that variation in social biology influences traits of the circadian clock.

Profiles of novel diurnally regulated genes in mouse hypothalamus: Expression analysis of the cysteine and histidine-rich domain-containing, zinc-binding protein 1, the fatty acid-binding protein 7 and the GTPase, ras-like family member 11b

Gene expression profiling of suprachiasmatic nucleus, ventrolateral preoptic area and the lateral hypothalamus was used to identify genes regulated diurnally in the hypothalamus of Mus musculus. The putative transcription regulator, cysteine and histidine-rich domain-containing, zinc binding protein 1, which had not been previously described in brain, was found to cycle diurnally in hypothalamus and forebrain with peak levels of mRNA expression during the dark phase. mRNA for the brain-type fatty acid binding protein 7 was found to change rhythmically in hypothalamic and extra-hypothalamic brain regions reaching peak levels early in the light phase suggesting that lipid metabolism is under circadian regulation in astrocytes. Rhythmically expressed genes in suprachiasmatic nucleus identified here were compared with previous reports in a meta-analysis. Genes held in common included fabp7, and the period gene, Per2. Also identified were genes implicated in guanosine-mediated signaling pathways that included dexamethasone-induced ras-related protein one ( dexras1), regulator of G-protein signaling ( rgs) 16, and ras-like family member 11b. Northern blotting confirmed diurnal changes in mRNA expression in the hypothalamus for these genes. Ras-like family member 11b was examined in more detail using in situ hybridization and antiphase diurnal changes in expression in suprachiasmatic nucleus and arcuate nucleus were identified implicating the gene in circadian-related, guanosine-mediated signaling. The transcription transactivator protein, CBP/p300-interacting transactivators with glutamic acid/aspartic acid-rich carboxyl-terminal domain, which had not been previously identified in brain, was enriched in suprachiasmatic nucleus and discrete regions of the hypothalamus and forebrain. The potential regulatory role of CBP/p300-interacting transactivators with glutamic acid/aspartic acid-rich carboxyl-terminal domain in the transcription of genes like TGF-α implicates the protein in diurnal activity rhythms. These results demonstrate the ability of gene expression profiling to identify potential candidates important in circadian or homeostatic processes.

Shortened Seasonal Photoperiodic Cycles Accelerate Aging of the Diurnal and Circadian Locomotor Activity Rhythms in a Primate

The gray mouse lemur (Microcebus murinus), a prosimian primate, exhibits seasonal rhythms strictly controlled by photoperiodic variations. Previous studies indicated that longevity can be altered by long-term acceleration of seasonal rhythms, providing a model for assessing various aspects of aging. To assess the effect of aging and accelerated aging on the circadian system of this primate, we compared the circadian rhythm of the locomotor activity in adult mouse lemurs (2-4.5 years, n = 9), aged mouse lemurs (5-9 years, n = 10), and adult mouse lemurs that had been exposed from birth to a shortened seasonal photoperiodic cycle (2-4.5 years, n = 7). Compared to adult animals, aged mouse lemurs showed a significant increase in intradaily variability and an advanced activity onset. Aging was characterized by a decrease in amplitude, with both a decrease in nocturnal activity and an increase in daytime activity. When maintained in constant dim red light, aged animals exhibited a shortening of the free-running period (22.8 +/- 0.1 h) compared to adult animals (23.5 +/- 0.1 h). A 3- to 5-year exposure to an accelerated seasonal photoperiodic rhythm ("annual" duration of 5 months) in accelerated mouse lemurs produced disturbances of the locomotor activity rhythm that resembled those of aged mouse lemurs, whether animals were studied in entrained or in free-running conditions. The present study demonstrated a weakened and fragmented locomotor activity rhythm during normal aging in this primate. Increasing the number of expressed seasonal cycles accelerated aging of parameters related to circadian rhythmicity in adult animals.

Summertime activity patterns of common weaselsMustela nivalis vulgaris under differing prey abundances in grassland habitats

WeaselsMustela nivalis Linnaeus, 1766 in Kielder Forest, UK showed a diurnal rhythm of activity in summer and we argue that this is the prevailing rhythm found in weasels under natural conditions. Climatic conditions influenced weasel activity with weasels decreasing activity under rainy conditions, but we found no influence of month or weasel weight. In certain habitat types levels of weasel activity increased with increasing field voleMicrotus agrestis density. This result stands in contrast to results from studies carried out in the laboratory and may reflect a greater proportion of time spent in reproductive activity and intra-specific interactions in areas where vole density, and hence conspecific density is high.

The early life history of tissue oxygenation in crustaceans: the strategy of the myodocopid ostracodCylindroleberis mariae

We studied basic principles of respiratory physiology in Cylindroleberididae, Cylindroleberis mariae Baird 1850, which are millimetre-sized crustaceans (myodocop ostracod) having a fossil record dating back to about 425 millions years ago. Facing experimental changes of O2 partial pressures in the range 2-40 kPa (normoxia is 21 kPa), C. mariae lack any regulatory mechanism to adapt their ventilatory and circulatory activity. Thus, the oxygenation status of their internal milieu must follow, as a dependent variable, the ambient oxygenation. Freely behaving C. mariae exhibit a marked diurnal activity rhythm. They are actively swimming in the water column during night, where they inspire in normoxic-normocapnic water. They are resting in self-made nests during daytime, where they are rebreathing in a confined and hypoxic environment. By analogy to extensive previous literature data, we suggest that these changes of respiratory gas content, and the associated tissue gas status, participate to the shaping of their metabolic activity and behaviour. To conclude, as Cylindroleberididae are early crustaceans exhibiting a remarkable stasis since the Palaeozoic, present data illustrates how principles of tissue oxygenation strategy can cover an impressive time scale.

Mating Activity of the Mammalophilic BlackliesSimulium (Wilhelmia) Lineatum(Meigen, 1804) (Diptera: Simuliidae) Under Laboratory Conditions

The diurnal rhythm of mating activity of the blackflies Simulium (W.) lineatum was established: 88–94% of insects were ready to mate during the daytime (6:00 a.m. – 7:00 p.m.), and 29–53% at night-time (9:00 p.m. – 4:00 a.m.). The peak of mating activity is predetermined by the rhythm of adult emergence from pupae with the time lag not longer than 2–3 hours. Until blood feeding, females mate only once while males copulate more times. Virgin blackflies copulated for 5.51 min at 26–28°C and 4.36 min at 29–32°C. When a male mated the 2nd time in a minute after the 1st mating, copulation lasted much longer, 12.98 min (at 26–28°C). The duration of both matings was the same with the interval between matings being within 17.3 to 22.5 hours. During copulation only a single spermatophore was transferred to a female. The length and width of the spermatophore transferred during the 1st copulation was 0.194 and 0.191 mm, respectively. The spermatophore transferred during the second copulation either 1 min or 24 hours...

Effects of pair housing on diurnal rhythms of heart rate and heart rate variability in miniature swine.

This study investigated the effects of pair housing on diurnal rhythms of heart rate and autonomic nervous activity in miniature swine. For this purpose, six adult Göttingen miniature swine were initially housed individually in an animal cage. Then, two of each swine were housed in a large cage together for 3 weeks. After that swine were separated into individual cages again. During this experimental procedure, electrocardiogram (ECG) was recorded with a Holter ECG recorder. Autonomic nervous activity was evaluated by power spectral analysis of heart rate variability. Heart rate and autonomic nervous activity clearly showed a diurnal rhythm in miniature swine housed in individual cages. When two swine were housed together, heart rate was significantly increased throughout the day and diurnal rhythm disappeared. Although these changes gradually recovered to basal levels, these parameters had not completely returned to basal levels even after 2 weeks. Heart rate was still higher than the initial level just after swine were re-housed in their own individual cages. Heart rate and autonomic nervous activity returned to basal levels about 2 weeks after re-housing. Further, heart rate in some swine decreased below their initial levels. These results suggest that it takes miniature swine at least 2 weeks to adapt to different circumstances. Furthermore, the power spectral analysis of heart rate variability can be used as a useful method in a study for answering controversial issues related to stress response.