Circadian rhythm in rat retinal dopamine

Rat retinal dopamine concentration and synthetic rate exhibit a circadian rhythm that persists in the absence of time cues. Although the population of retinal amacrine cells containing dopamine is small, retinal dopamine neurones may lie on the pathway mediating light information to the circadian system.     

Circadian activity rhythm in demented and non-demented nursing-home residents measured by telemetric actigraphy

There is a need to develop unobtrusive methods for long-term monitoring of sleep/wake and circadian activity patterns in the elderly both in nursing homes and at home settings as sleep is important for health and well-being. The IST Vivago WristCare is an active social alarm system, which provides continuous telemetric monitoring of the user's activity. We examined how the activity signal measured by IST Vivago differed between demented and non-demented subjects living in a nursing home, and how it correlated with the subjective assessment of sleep quality and daytime alertness. The activity signal data together with subjective assessments of sleep quality and daytime vigilance were collected from 42 volunteers (aged 56-97 years; 23 demented and 19 non-demented) for at least 10 days. The demented subjects had lower daytime activity and higher nocturnal activity than the non-demented subjects. Correlations between the activity parameters and self-assessments were weak but statistically significant. We also found correlation between functional ability and diurnal activity. The results are in line with previous studies with demented and non-demented elderly subjects and suggest that the IST Vivago system provides a valid instrument for unobtrusive continuous long-term monitoring of the circadian rhythm and sleep/wake patterns in the elderly.     

Circadian rhythm of response of mouse lingual and esophageal epithelial cells to hydroxyurea

Department of Biology, Medico-biological Faculty, N. I. Pirogov Second Moscow Medical Institute. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 108, No. 11, pp. 612–613, November, 1989.     

Sleep–wake rhythm disturbances and perceived sleep in adolescent chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is characterized by long‐lasting, disabling and unexplained fatigue that is often accompanied by unrefreshing sleep. The aim of this cross‐sectional study was to investigate sleep–wake rhythm and perceived sleep in adolescent CFS patients compared to healthy individuals. We analysed baseline data on 120 adolescent CFS patients and 39 healthy individuals included in the NorCAPITAL project. Activity measures from a uniaxial accelerometer (activPAL) were used to estimate mid‐sleep time (mid‐point of a period with sleep) and time in bed. Scores from the Karolinska Sleep Questionnaire (KSQ) were also assessed. The activity measures showed that the CFS patients stayed significantly longer in bed, had a significantly delayed mid‐sleep time and a more varied sleep–wake rhythm during weekdays compared with healthy individuals. On the KSQ, the CFS patients reported significantly more insomnia symptoms, sleepiness, awakening problems and a longer sleep onset latency than healthy individuals. These results might indicate that disrupted sleep–wake phase could contribute to adolescent CFS; however, further investigations are warranted.     

冠状动脉搭桥术病人围术期皮质醇分泌的昼夜节律性

观察冠状动脉搭桥术病人围术期皮质醇昼夜分泌节律性的变化。选择在低温体外循环或非体外循环下行冠脉搭桥术的男性病人40例，分为体外循环组和非体外循环组，每组20例。所有病人均在麻醉诱导前(基础值)、气管插管后。10min、肝素化后10min、转机后30min(或切皮后2h)、中和肝素前和术终各时点及术后每3h抽血1次持续到术后24h。采用放射免疫方法检测血浆皮质醇的浓度。两组病人术中各时点血浆皮质醇浓度显著低于麻醉诱导前，而在术后24h明显升高；非体外循环组病人在诱导后和术终时点皮质醇水平高于体外循环组。在术后24h体外循环组与非体外循环组分别有3例和7例病人的皮质醇分泌表现为昼夜节律性，其余病人则无昼夜节律性分泌。体外循环与非体外循环冠状动脉搭桥术后多数病人皮质醇昼夜节律性分泌紊乱，但非体外循环冠脉搭桥术病人术后早期有皮质醇昼夜分泌节律性的病例数多于体外循环组，提示体外循环有可能干扰了围术期皮质醇的分泌节律。     

Circadian rhythm of phospholipid content and nonspecific phosphomonoesterase activity in the rat liver

A circadian rhythm of the content of total and individual phospholipids and of alkaline and acid phosphatase activity was found in the albino rat liver by biochemical and histochemical methods. The phospholipid content and enzyme activity were higher during the daytime (9 a.m. to 3 p.m.). The results indicate harmony between the structural and metabolic organization of the liver during the period of maximal functioning activity of the organ.Central Research Laboratory, Tyumen' Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 11, pp. 604–607, November, 1979.     

Fragmentation of the rest-activity rhythm correlates with age-related cognitive deficits

Aging affects both cognitive performance and the sleep-wake rhythm. The recent surge of studies that support a role of sleep for cognitive performance in healthy young adults suggests that disturbed sleep-wake rhythms may contribute to 'age-related' cognitive decline. This relationship has however not previously been extensively investigated. The present correlational study integrated a battery of standardized cognitive tests to investigate the association of mental speed, memory, and executive function with actigraphically recorded sleep-wake rhythms in 144 home-dwelling elderly participants aged 69.5 ± 8.5 (mean ± SD). Multiple regression analyses showed that the partial correlations of the fragmentation of the sleep-wake rhythm with each of the three cognitive domains ( r  = −0.16, −0.19, and −0.16 respectively) were significant. These associations were independent from main effects of age, implying that a unique relationship between the rest-activity rhythm and cognitive performance is present in elderly people.     

Circadian rhythm of wrist temperature in normal-living subjects A candidate of new index of the circadian system

Most circadian rhythms are under the control of a major pacemaker located in the hypothalamic suprachiasmatic nucleus. Some of these rhythms, called marker rhythms, serve to characterize the timing of the internal temporal order. A marker rhythm, (e.g., one used in chronotherapy) has to be periodic and easy to measure over long periods using non-invasive methods. The most frequent reference variables for human chronotherapy include salivary melatonin or cortisol, urinary 6-sulfatoximelatonin, actimetry and core body temperature (CBT). Recent evidence suggests that sleepiness may be more closely linked to increased peripheral skin temperature than to a core temperature drop, and that distal skin temperature seems to be correlated and phase-advanced with respect to CBT, suggesting that heat loss from the extremities may drive the circadian CBT rhythm.The aim of the present study was to evaluate whether the wrist skin temperature rhythm could be used as a possible index of the human circadian system. To this end, wrist skin temperature (WT1), as determined by a wireless data logger in healthy normal living subjects, was correlated with sleep-wake diaries and oral temperature (OT) recordings. WT and sleep habits were studied in 99 university students. Each subject wore a wireless iButton sensor attached to the inner side of a sport wristband. Our results show that the WT rhythm exhibits an inverse phase relationship with OT, and it is phase-advanced by 60 min with respect to OT. WT started to increase in association to bed time and dropped sharply after awakening. A secondary WT increase, independent of feeding, was observed in the early afternoon.In conclusion, WT wireless recording can be considered a reliable procedure to evaluate circadian rhythmicity, and an index to establish and follow the effects of chronotherapy in normal living subjects.     

Circadian rhythm sleep disorders: part II, advanced sleep phase disorder, delayed sleep phase disorder, free-running disorder, and irregular sleep-wake rhythm. An American Academy of Sleep Medicine review

OBJECTIVE: This the second of two articles reviewing the scientific literature on the evaluation and treatment of circadian rhythm sleep disorders (CRSDs), employing the methodology of evidence-based medicine. We herein report on the accumulated evidence regarding the evaluation and treatment of Advamced Sleep Phase Disorder (ASPD), Delayed Sleep Phase Disorder (DSPD), Free-Running Disorder (FRD) and Irregular Sleep-Wake Rhythm ISWR). METHODS: A set of specific questions relevant to clinical practice were formulated, a systematic literature search was performed, and relevant articles were abstracted and graded. RESULTS: A substantial body of literature has accumulated that provides a rational basis the evaluation and treatment of CRSDs. Physiological assessment has involved determination of circadian phase using core body temperature and the timing of melatonin secretion. Behavioral assessment has involved sleep logs, actigraphy and the Morningness-Eveningness Questionnaire (MEQ). Treatment interventions fall into three broad categories: 1) prescribed sleep scheduling, 2) circadian phase shifting ("resetting the clock"), and 3) symptomatic treatment using hypnotic and stimulant medications. CONCLUSION: Circadian rhythm science has also pointed the way to rational interventions for CRSDs and these treatments have been introduced into the practice of sleep medicine with varying degrees of success. More translational research is needed using subjects who meet current diagnostic criteria.     

Sleep loss-related decrements in planning performance in healthy elderly depend on task difficulty

Prefrontal cortex (PFC)-related functions are particularly sensitive to sleep loss. However, their repeated examination is intricate because of methodological constraints such as practice effects and loss of novelty. We investigated to what extent the circadian timing system and the sleep homeostat influence PFC-related performance in differently difficult versions of a single task. Parallel versions of a planning task combined with a control group investigation were used to control for practice effects. Thirteen healthy volunteers (five women and eight men, range 57-74 years) completed a 40-h sleep deprivation (SD) and a 40-h multiple nap protocol (NAP) under constant routine conditions. Each participant performed 11 easy and 11 difficult task versions under either SD or NAP conditions. The cognitive and motor components of performance could be distinguished and analysed separately. Only by thoroughly controlling for superimposed secondary factors such as practice or sequence effects, could a significant influence of circadian timing and sleep pressure be clearly detected in planning performance in the more difficult, but not easier maze tasks. These results indicate that sleep loss-related decrements in planning performance depend on difficulty level, and that apparently insensitive tasks can turn out to be sensitive to sleep loss and circadian variation.     

The 24-h growth hormone rhythm in men: sleep and circadian influences questioned

The 24-h rhythm of growth hormone (GH) is thought to be controlled primarily by sleep processes with a weak circadian component. This concept has been recently questioned in sleep-deprived persons. To test the notion of a high sleep-dependency of GH release, we established simultaneous 24-h rhythms of GH and melatonin, a circadian marker, in night workers who form a model for challenging sleep and circadian processes. Ten day-active subjects and 11 night workers were studied during their usual sleep-wake schedule, with sleep from 23:00 to 07:00 hours and 07:00 to 15:00 hours, respectively. Experiments were conducted in sleep rooms under continuous nutrition, bed rest, and dim light. Melatonin and GH were measured every 10 min over 24 h. In day-active subjects, melatonin and GH showed the well-known 24-h profiles, with a major sleep-related GH pulse accounting for 52.8 +/- 3.5% of the 24-h GH production and the onset of the melatonin surge occurring at 21:53 hours +/- 18 min. In night workers, melatonin showed variable circadian adaptation, with the onset of secretion varying between 21:45 and 05:05 hours. The sleep-related GH pulse was lowered, but the reduction was compensated for by the emergence of large individual pulses occurring unpredictably during waking periods, so that the total amount of GH secreted during the 24 h was constant. One cannot predict the degree of GH adaptation from the highly variable melatonin shift. These results argue against the concept that sleep processes exert a predominant influence on GH release whatever the conditions. When sleep and circadian processes are misaligned, the blunting of the sleep-related GH pulse is counteracted, as in sleep-deprived persons, by a compensatory mechanism promoting GH pulses during wakefulness.     

Circadian rhythm in metabolic activity of suprachiasmatic, supraoptic and raphe nuclei

Previous studies using 2-deoxyglucose (2-DG) autoradiography have demonstrated that the suprachiasmatic nucleus (SCN) of the hypothalamus, a putative neural circadian pacemaker, displays circadian rhythmicity in its metabolic activity. In the present study, we show that distinct circadian variations in 2-DG uptake occur not only in the suprachiasmatic, but also in the supraoptic and median raphe nuclei of the rat brain. On the other hand, several other brain areas failed to display systematic circadian variations in 2-DG uptake. These results indicate that circadian metabolic rhythms are not unique to the SCN. Further studies are required to precisely define the extent of such phenomena.     

Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders. An American Academy of Sleep Medicine review

OBJECTIVE: This the first of two articles reviewing the scientific literature on the evaluation and treatment of circadian rhythm sleep disorders (CRSDs), employing the methodology of evidence-based medicine. In this first part of this paper, the general principles of circadian biology that underlie clinical evaluation and treatment are reviewed. We then report on the accumulated evidence regarding the evaluation and treatment of shift work disorder (SWD) and jet lag disorder (JLD). METHODS: A set of specific questions relevant to clinical practice were formulated, a systematic literature search was performed, and relevant articles were abstracted and graded. RESULTS: A substantial body of literature has accumulated that provides a rational basis the evaluation and treatment of SWD and JLD. Physiological assessment has involved determination of circadian phase using core body temperature and the timing of melatonin secretion. Behavioral assessment has involved sleep logs, actigraphy and the Morningness-Eveningness Questionnaire (MEQ). Treatment interventions fall into three broad categories: 1) prescribed sleep scheduling, 2) circadian phase shifting ("resetting the clock"), and 3) symptomatic treatment using hypnotic and stimulant medications. CONCLUSION: Circadian rhythm science has also pointed the way to rational interventions for the SWD and JLD, and these treatments have been introduced into the practice of sleep medicine with varying degrees of success. More translational research is needed using subjects who meet current diagnostic criteria.     

Effects of prolonged wakefulness on cyclic alternating pattern (CAP) during sleep recovery at different circadian phases

Two separate groups of healthy subjects aged between 20 and 30 years underwent a random sequence of two non-consecutive polysomnographic recordings under standard conditions (night basal sleep) and after continuous sleep deprivation (recovery sleep). In the first group of 6 subjects (3 males and 3 females) recovery sleep occurred in the morning (after 24 h of prior waking); in the second group of 6 subjects (3 males and 3 females) recovery sleep occurred in the night (after 36 h of prior waking). In all cases the recording time was restricted to 500 minutes. Scoring was accomplished on conventional sleep variables and on Cyclic Alternating Pattern (CAP) parameters, while statistical analysis was based on a 2 x 2 ANOVA test. Compared to the night basal conditions, total sleep time and total NREM sleep were significantly longer in night recovery sleep and shorter in morning recovery sleep, respectively. No significant differences were found for sleep latency, intra-sleep awakenings, stage 2, REM sleep, NREM stages and slow-wave sleep. Total CAP time, CAP time in slow-wave sleep and all CAP rates were significantly higher in morning recovery sleep and lower in night recovery sleep. The enhanced amounts of CAP time and CAP rates during morning recovery sleep may be the outcome of two opposite forces, i.e. high sleep pressure versus maximum wake propensity. In contrast, the lower values of CAP during night recovery sleep suggest an in-phase associations between strong sleep pressure and the circadian clock.