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1

Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons  

E-print Network

Intrinsic, nondeterministic circadian rhythm generation in identified mammalian neurons Alexis B August 5, 2009 (received for review March 16, 2009) Circadian rhythms are modeled as reliable and self the hypothesis that circadian cycling is intrinsic to a unique class of SCN neurons by measuring firing rate

Huettner, James E.

2

Circadian Rhythms  

MedlinePLUS

... get drowsy. How are circadian rhythms related to jet lag? Jet lag occurs when travelers suffer from disrupted circadian rhythms. ... may lead researchers to treatments for sleep disorders, jet lag and other health problems. Learning more about the ...

3

CIRCADIAN RHYTHMS Circadian Photoreception  

NSDL National Science Digital Library

The circadian rhythms of physiology and behavior are driven by autonomous cellular clocks. To be useful, these clocks must be synchronized to the day-night cycles of the real world. This article provides a review of research on circadian photoreceptors in mammals.

Michael Menaker (University of Virginia; Department of Biology)

2003-01-10

4

Biological Clocks & Circadian Rhythms  

ERIC Educational Resources Information Center

The study of biological clocks and circadian rhythms is an excellent way to address the inquiry strand in the National Science Education Standards (NSES) (NRC 1996). Students can study these everyday phenomena by designing experiments, gathering and analyzing data, and generating new experiments. As students explore biological clocks and circadian

Robertson, Laura; Jones, M. Gail

2009-01-01

5

Sleep and circadian rhythms  

NASA Technical Reports Server (NTRS)

Three interacting processes are involved in the preservation of circadian rhythms: (1) endogenous rhythm generation mechanisms, (2) entrainment mechanisms to keep these rhythms 'on track', and (3) exogenous masking processes stemming from changes in environment and bahavior. These processes, particularly the latter two, can be dramatically affected in individuals of advanced age and in space travelers, with a consequent disruption in sleep and daytime functioning. This paper presents results of a phase-shift experiment investigating the age-related effects of the exogeneous component of circadian rhythms in various physiological and psychological functions by comparing these functions in middle aged and old subjects. Dramatic differences were found between the two age groups in measures of sleep, mood, activation, and performance efficiency.

Monk, Timothy H.

1991-01-01

6

Circadian Rhythm Sleep Disorders  

PubMed Central

There have been remarkable advances in our understanding of the molecular, cellular and physiological mechanisms underlying the regulation of circadian rhythms, as well as the impact of circadian dysfunction on health and disease. This information has transformed our understanding of the effect of circadian rhythm sleep disorders (CRSD) on health, performance and safety. CRSDs are caused by alterations of the central circadian time-keeping system, or a misalignment of the endogenous circadian rhythm and the external environment. In this section, we provide a review of circadian biology and discuss the pathophysiology, clinical features, diagnosis, and treatment of the most commonly encountered CRSDs in clinical practice. PMID:23099133

Zhu, Lirong; Zee, Phyllis C.

2012-01-01

7

Biological Clocks and Circadian Rhythms  

NSDL National Science Digital Library

The study of biological clocks and circadian rhythms is an excellent way to address the inquiry strand in the National Science Education Standards (NSES) (NRC 1996). Students can study these everyday phenomena by designing experiments, gathering and analyzing data, and generating new experiments. As students explore biological clocks and circadian rhythms, they are provided with opportunities to connect learning to experiences and observations from their own lives. This article describes how to reset the biological clock of a shamrock plant while shedding light on its circadian rhythms.

Laura Robertson

2009-02-01

8

Circadian Rhythm Abnormalities  

PubMed Central

Purpose: This article reviews the recent advances in understanding of the fundamental properties of circadian rhythms and discusses the clinical features, diagnosis, and treatment of circadian rhythm sleep disorders (CRSDs). Recent Findings: Recent evidence strongly points to the ubiquitous influence of circadian timing in nearly all physiologic functions. Thus, in addition to the prominent sleep and wake disturbances, circadian rhythm disorders are associated with cognitive impairment, mood disturbances, and increased risk of cardiometabolic disorders. The recent availability of biomarkers of circadian timing in clinical practice has improved our ability to identify and treat these CRSDs. Summary: Circadian rhythms are endogenous rhythms with a periodicity of approximately 24 hours. These rhythms are synchronized to the physical environment by social and work schedules by various photic and nonphotic stimuli. CRSDs result from a misalignment between the timing of the circadian rhythm and the external environment (eg, jet lag and shift work) or a dysfunction of the circadian clock or its afferent and efferent pathways (eg, delayed sleep-phase, advanced sleep-phase, non–24-hour, and irregular sleep-wake rhythm disorders). The most common symptoms of these disorders are difficulties with sleep onset and/or sleep maintenance and excessive sleepiness that are associated with impaired social and occupational functioning. Effective treatment for most of the CRSDs requires a multimodal approach to accelerate circadian realignment with timed exposure to light, avoidance of bright light at inappropriate times, and adherence to scheduled sleep and wake times. In addition, pharmacologic agents are recommended for some of the CRSDs. For delayed sleep-phase, non–24-hour, and shift work disorders, timed low-dose melatonin can help advance or entrain circadian rhythms; and for shift work disorder, wake-enhancing agents such as caffeine, modafinil, and armodafinil are options for the management of excessive sleepiness. PMID:23385698

Zee, Phyllis C.; Attarian, Hrayr; Videnovic, Aleksandar

2013-01-01

9

Measuring stem cell circadian rhythm.  

PubMed

Circadian rhythms are biological rhythms that occur within a 24-h time cycle. Sleep is a prime example of a circadian rhythm and with it melatonin production. Stem cell systems also demonstrate circadian rhythms. This is particularly the case for the proliferating cells within the system. In fact, all proliferating cell populations exhibit their own circadian rhythm, which has important implications for disease and the treatment of disease. Stem cell chronobiology is particularly important because the treatment of cancer can be significantly affected by the time of day a drug is administered. This protocol provides a basis for measuring hematopoietic stem cell circadian rhythm for future stem cell chronotherapeutic applications. PMID:25388388

Hrushesky, William; Rich, Ivan N

2015-01-01

10

[Circadian rhythm sleep disorder].  

PubMed

Primary pathophysiology of circadian rhythm sleep disorders(CRSDs) is a misalignment between the endogenous circadian rhythm phase and the desired or socially required sleep-wake schedule, or dysfunction of the circadian pacemaker and its afferent/efferent pathways. CRSDs consist of delayed sleep phase type, advanced sleep phase type, free-running type, irregular sleep-wake type, shift work type and jet lag type. Chronotherapy using strong zeitgebers (time cues), such as bright light and melatonin/ melatonin type 2 receptor agonist, is effective when administered with proper timing. Bright light is the strongest entraining agent of circadian rhythms. Bright light therapy (appropriately-timed exposure to bright light) for CRSDs is an effective treatment option, and can shift the sleep-wake cycle to earlier or later times, in order to correct for misalignment between the circadian system and the desired sleep-wake schedule. Timed administration of melatonin, either alone or in combination with light therapy has also been shown to be useful in the treatment of CRSDs. PMID:24437262

Mishima, Kazuo

2013-12-01

11

Circadian Rhythm Sleep Disorders  

PubMed Central

Objective To review circadian rhythm sleep disorders, including underlying causes, diagnostic considerations, and typical treatments. Methods Literature review and discussion of specific cases. Results Survey studies 1,2 suggest that up to 3% of the adult population suffers from a circadian rhythm sleep disorder (CRSD). However, these sleep disorders are often confused with insomnia, and an estimated 10% of adult and 16% of adolescent sleep disorders patients may have a CRSD 3-6. While some CRSD (such as jet lag) can be self-limiting, others when untreated can lead to adverse medical, psychological, and social consequences. The International Classification of Sleep Disorders classifies CRSD as dyssomnias, with six subtypes: Advanced Sleep Phase Type, Delayed Sleep Phase Type, Irregular Sleep Wake Type, Free Running Type, Jet Lag Type, and Shift Work Type. The primary clinical characteristic of all CRSD is an inability to fall asleep and wake at the desired time. It is believed that CRSD arise from a problem with the internal biological clock (circadian timing system) and/or misalignment between the circadian timing system and the external 24-hour environment. This misalignment can be the result of biological and/or behavioral factors. CRSD can be confused with other sleep or medical disorders. Conclusions Circadian rhythm sleep disorders are a distinct class of sleep disorders characterized by a mismatch between the desired timing of sleep and the ability to fall asleep and remain asleep. If untreated, CRSD can lead to insomnia and excessive daytime sleepiness, with negative medical, psychological, and social consequences. It is important for physicians to recognize potential circadian rhythm sleep disorders so that appropriate diagnosis, treatment, and referral can be made. PMID:25368503

Kim, Min Ju; Lee, Jung Hie; Duffy, Jeanne F.

2014-01-01

12

CHAPTER SEVEN Circadian Rhythms, Sleep  

E-print Network

CHAPTER SEVEN Circadian Rhythms, Sleep Deprivation, and Human Performance Namni Goel*, Mathias, Philadelphia, Pennsylvania, USA Contents 1. Introduction 156 2. Sleep­Wake and Circadian Regulation: Two-Process Model 157 3. Circadian Rhythms of Performance 162 3.1 Subjective measures of sleepiness and alertness

Pennsylvania, University of

13

Robustness of circadian rhythms with respect to molecular noise  

E-print Network

Robustness of circadian rhythms with respect to molecular noise Didier Gonze, Jose´ Halloy molecular model capable of generating circadian rhythms to assess the robustness of circadian oscillations on the expression of its gene. Such a negative regulatory mechanism underlies circadian oscillations of the PER

Goldbeter, Albert

14

Circadian rhythm and its role in malignancy  

PubMed Central

Circadian rhythms are daily oscillations of multiple biological processes directed by endogenous clocks. The circadian timing system comprises peripheral oscillators located in most tissues of the body and a central pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Circadian genes and the proteins produced by these genes constitute the molecular components of the circadian oscillator which form positive/negative feedback loops and generate circadian rhythms. The circadian regulation extends beyond clock genes to involve various clock-controlled genes (CCGs) including various cell cycle genes. Aberrant expression of circadian clock genes could have important consequences on the transactivation of downstream targets that control the cell cycle and on the ability of cells to undergo apoptosis. This may lead to genomic instability and accelerated cellular proliferation potentially promoting carcinogenesis. Different lines of evidence in mice and humans suggest that cancer may be a circadian-related disorder. The genetic or functional disruption of the molecular circadian clock has been found in various cancers including breast, ovarian, endometrial, prostate and hematological cancers. The acquisition of current data in circadian clock mechanism may help chronotherapy, which takes into consideration the biological time to improve treatments by devising new therapeutic approaches for treating circadian-related disorders, especially cancer. PMID:20353609

2010-01-01

15

Studying circadian rhythms in Drosophila melanogaster.  

PubMed

Circadian rhythms have a profound influence on most bodily functions: from metabolism to complex behaviors. They ensure that all these biological processes are optimized with the time-of-day. They are generated by endogenous molecular oscillators that have a period that closely, but not exactly, matches day length. These molecular clocks are synchronized by environmental cycles such as light intensity and temperature. Drosophila melanogaster has been a model organism of choice to understand genetically, molecularly and at the level of neural circuits how circadian rhythms are generated, how they are synchronized by environmental cues, and how they drive behavioral cycles such as locomotor rhythms. This review will cover a wide range of techniques that have been instrumental to our understanding of Drosophila circadian rhythms, and that are essential for current and future research. PMID:24412370

Tataroglu, Ozgur; Emery, Patrick

2014-06-15

16

METABOLISM AND THE CONTROL OF CIRCADIAN RHYTHMS  

E-print Network

METABOLISM AND THE CONTROL OF CIRCADIAN RHYTHMS Jared Rutter, Martin Reick, and Steven L. Mc@biochem.swmed.edu Key Words entrainment, suprachiasmatic nucleus, circadian rhythm, neural activity, restricted feeding, central circadian oscillator f Abstract The core apparatus that regulates circadian rhythm has been exten

Rutter, Jared

17

CIRCADIAN RHYTHM DISTURBANCES IN DEPRESSION  

PubMed Central

Objective The aim of this article is to review progress in understanding the mechanisms that underlie circadian and sleep rhythms, and their role in the pathogenesis and treatment of depression. Methods Literature was selected principally by Medline searches, and additional reports were identified based on ongoing research activities in the authors’ laboratory. Results Many physiological processes show circadian rhythms of activity. Sleep and waking are the most obvious circadian rhythms in mammals. There is considerable evidence that circadian and sleep disturbances are important in the pathophysiology of mood disorders. Depressed patients often show altered circadian rhythms, sleep disturbances, and diurnal mood variation. Chronotherapies, including bright light exposure, sleep deprivation, and social rhythm therapies, may be useful adjuncts in non-seasonal and seasonal depression. Antidepressant drugs have marked effects on circadian processes and sleep. Conclusions Recent progress in understanding chronobiological and sleep regulation mechanisms may provide novel insights and avenues into the development of new pharmacological and behavioral treatment strategies for mood disorders. PMID:18680211

Germain, Anne; Kupfer, David J.

2008-01-01

18

Circadian rhythms in the green sunfish retina  

PubMed Central

We investigated the occurrence of circadian rhythms in retinomotor movements and retinal sensitivity in the green sunfish, Lepomis cyanellus. When green sunfish were kept in constant darkness, cone photoreceptors exhibited circadian retinomotor movements; rod photoreceptors and retinal pigment epithelium (RPE) pigment granules did not. Cones elongated during subjective night and contracted during subjective day. These results corroborate those of Burnside and Ackland (1984. Investigative Ophthalmology and Visual Science. 25:539-545). Electroretinograms (ERGs) recorded in constant darkness in response to dim flashes (lambda = 640 nm) exhibited a greater amplitude during subjective night than during subjective day. The nighttime increase in the ERG amplitude corresponded to a 3-10-fold increase in retinal sensitivity. The rhythmic changes in the ERG amplitude continued in constant darkness with a period of approximately 24 h, which indicates that the rhythm is generated by a circadian oscillator. The spectral sensitivity of the ERG recorded in constant darkness suggests that cones contribute to retinal responses during both day and night. Thus, the elongation of cone myoids during the night does not abolish the response of the cones. To examine the role of retinal efferents in generating retinal circadian rhythms, we cut the optic nerve. This procedure did not abolish the rhythms of retinomotor movement or of the ERG amplitude, but it did reduce the magnitude of the nighttime phases of both rhythms. Our results suggest that more than one endogenous oscillator regulates the retinal circadian rhythms in green sunfish. Circadian signals controlling the rhythms may be either generated within the eye or transferred to the eye via a humoral pathway. PMID:3598559

1987-01-01

19

Melatonin for Circadian Rhythm Disturbances in Dementia  

E-print Network

Melatonin for Circadian Rhythm Disturbances in Dementia Available from: http of melatonin in dementia 4. Determine melatonin's role in the treatment of circadian rhythm disturbances in dementia #12;Payton H Melatonin for circadian rhythm disturbances in dementia Page 2 I. Dementia a

Pillow, Jonathan

20

Circadian Rhythm Control: Neurophysiological Investigations  

NASA Technical Reports Server (NTRS)

The suprachiasmatic nucleus (SCN) was implicated as a primary component in central nervous system mechanisms governing circadian rhythms. Disruption of the normal synchronization of temperature, activity, and other rhythms is detrimental to health. Sleep wake disorders, decreases in vigilance and performance, and certain affective disorders may result from or be exacerbated by such desynchronization. To study the basic neurophysiological mechanisms involved in entrainment of circadian systems by the environment, Parylene-coated, etched microwire electrode bundles were used to record extracellular action potentials from the small somata of the SCN and neighboring hypothalamic nuclei in unanesthetized, behaving animals. Male Wistar rats were anesthetized and chronically prepared with EEG ane EMG electrodes in addition to a moveable microdrive assembly. The majority of cells had firing rates 10 Hz and distinct populations of cells which had either the highest firing rate or lowest firing rate during sleep were seen.

Glotzbach, S. F.

1985-01-01

21

Circadian Rhythm Disruption in Cancer Biology  

PubMed Central

Circadian rhythms show universally a 24-h oscillation pattern in metabolic, physiological and behavioral functions of almost all species. This pattern is due to a fundamental adaptation to the rotation of Earth around its own axis. Molecular mechanisms of generation of circadian rhythms organize a biochemical network in suprachiasmatic nucleus and peripheral tissues, building cell autonomous clock pacemakers. Rhythmicity is observed in transcriptional expression of a wide range of clock-controlled genes that regulate a variety of normal cell functions, such as cell division and proliferation. Desynchrony of this rhythmicity seems to be implicated in several pathologic conditions, including tumorigenesis and progression of cancer. In 2007, the International Agency for Research on Cancer (IARC) categorized “shiftwork that involves circadian disruption [as] probably carcinogenic to humans” (Group 2A in the IARC classification system of carcinogenic potency of an agentagent) (Painting, Firefighting, and Shiftwork; IARC; 2007). This review discusses the potential relation between disruptions of normal circadian rhythms with genetic driving machinery of cancer. Elucidation of the role of clockwork disruption, such as exposure to light at night and sleep disruption, in cancer biology could be important in developing new targeted anticancer therapies, optimizing individualized chronotherapy and modifying lighting environment in workplaces or homes. PMID:22811066

Savvidis, Christos; Koutsilieris, Michael

2012-01-01

22

Circadian Rhythms in Drosophila: A Connections Map  

NSDL National Science Digital Library

Genetic and biochemical experiments over the past decade have allowed the construction of a viable working model for the molecular mechanisms underlying circadian rhythm generation in Drosophila. The basic mechanism consists of two intertwined transcription-translation negative feedback loops. One loop--the "positive loop"--controls the rhythmic expression of a Per-Arnt-Sim (PAS)-domain-containing positive transcription factor, Clock. The second loop--the "negative loop"--controls the transcription of period and timeless, two genes encoding repressor proteins. The loops are intertwined because Period and Timeless directly repress transcription mediated by the Clock:Cycle heterodimer, whereas Clock:Cycle drives transcription of period and timeless, as well as that of vrille, a repressor of Clock expression. Other proteins, including kinases encoded by doubletime, shaggy, Andante, and Timekeeper, also have essential functions in the timekeeping mechanism. Light cycles can synchronize the Drosophila circadian pathway by directly stimulating Cryptochrome-dependent degradation of Timeless. This Pathway Map of the Drosophila circadian mechanism describes the individual known components of the fly circadian clock and their mutual interactions. An accompanying animation schematizes the dynamic interactions of the different components. Science Viewpoint R. N. Van Gelder, E. D. Herzog, W. J. Schwartz, P. H. Taghert, Circadian rhythms: In the loop at last. Science 300, 1534-1535 (2003). [Abstract] [Full Text

Russell N. Van Gelder (Department of Molecular Biology and Pharmacology; Department of Ophthalmology and Visual Sciences REV)

2003-08-05

23

Circadian Rhythms and Cancer Chronotherapeutics  

Microsoft Academic Search

\\u000a The Circadian Timing System (CTS) controls cellular proliferation and drug metabolism over a 24-h period through molecular\\u000a clocks in each cell. These cellular clocks are coordinated by a hypothalamic pacemaker, the suprachiasmatic nuclei, which\\u000a generate or control circadian physiology. The CTS down-regulates malignant growth in experimental models and in cancer patients.\\u000a It also generates large and predictable 24-h changes in

Francis Lévi; Atilla Altinok; Albert Goldbeter

24

Circadian rhythms in myocardial metabolism and function  

Technology Transfer Automated Retrieval System (TEKTRAN)

Circadian rhythms in myocardial function and dysfunction are firmly established in both animal models and humans. For example, the incidence of arrhythmias and sudden cardiac death increases when organisms awaken. Such observations have classically been explained by circadian rhythms in neurohumoral...

25

CIRCADIAN RHYTHM REPROGRAMMING DURING LUNG INFLAMMATION  

PubMed Central

Circadian rhythms are known to regulate immune responses in healthy animals, but it is unclear whether they persist during acute illnesses where clock gene expression is disrupted by systemic inflammation. Here, we use a genome-wide approach to investigate circadian gene and metabolite expression in the lungs of endotoxemic mice and find that novel cellular and molecular circadian rhythms are elicited in this setting. The endotoxin-specific circadian program exhibits unique features, including a divergent group of rhythmic genes and metabolites compared to the basal state and a distinct periodicity and phase distribution. At the cellular level endotoxin treatment also alters circadian rhythms of leukocyte counts within the lung in a bmal1-dependent manner, such that granulocytes rather than lymphocytes become the dominant oscillating cell type. Our results show that inflammation produces a complex reorganization of cellular and molecular circadian rhythms that are relevant to early events in lung injury. PMID:25208554

Haspel, Jeffrey A.; Chettimada, Sukrutha; Shaik, Rahamthulla S.; Chu, Jen-Hwa; Raby, Benjamin A.; Cernadas, Manuela; Carey, Vincent; Process, Vanessa; Hunninghake, G. Matthew; Ifedigbo, Emeka; Lederer, James A.; Englert, Joshua; Pelton, Ashley; Coronata, Anna; Fredenburgh, Laura E.; Choi, Augustine M. K.

2014-01-01

26

Circadian rhythms: glucocorticoids and arthritis.  

PubMed

Circadian rhythms are driven by biological clocks and are endogenous in origin. Therefore, circadian changes in the metabolism or secretion of endogenous glucocorticoids are certainly responsible in part for the time-dependent changes observed in the inflammatory response and arthritis. More recently, melatonin (MLT), another circadian hormone that is the secretory product of the pineal gland, has been found implicated in the time-dependent inflammatory reaction with effects opposite those of cortisol. Interestingly, cortisol and MLT show an opposite response to the light. The light conditions in the early morning have a strong impact on the morning cortisol peak, whereas MLT is synthesized in a strictly nocturnal pattern. Recently, a diurnal rhythmicity in healthy humans between cellular (Th1 type) or humoral (Th2 type) immune responses has been found and related to immunomodulatory actions of cortisol and MLT. The interferon (IFN)-gamma/interleukin (IL)-10 ratio peaked during the early morning and correlated negatively with plasma cortisol and positively with plasma MLT. Accordingly, the intensity of the arthritic pain varies consistently as a function of the hour of the day: pain is greater after waking up in the morning than in the afternoon or evening. The reduced cortisol and adrenal androgen secretion, observed during testing in rheumatoid arthritis (RA) patients not treated with glucocoticoids, should be clearly considered as a "relative adrenal insufficiency" in the presence of a sustained inflammatory process, and allows Th1 type cytokines to be produced in higher amounts during the late night. In conclusion, the right timing (early morning) for the glucocorticoid therapy in arthritis is fundamental and well justified by the circadian rhythms of the inflammatory mechanisms. PMID:16855156

Cutolo, Maurizio; Sulli, Alberto; Pizzorni, Carmen; Secchi, Maria Elena; Soldano, Stefano; Seriolo, Bruno; Straub, Rainer H; Otsa, Kati; Maestroni, Georges J

2006-06-01

27

Circadian Rhythms in Cultured Mammalian Retina  

Microsoft Academic Search

Many retinal functions are circadian, but in most instances the location of the clock that drives the rhythm is not known. Cultured neural retinas of the golden hamster (Mesocricetus auratus) exhibited circadian rhythms of melatonin synthesis for at least 5 days at 27^circC. The rhythms were entrained by light cycles applied in vitro and were free-running in constant darkness. Retinas

Gianluca Tosini; Michael Menaker

1996-01-01

28

JOURNAL OF BIOLOGICAL RHYTHMS / December 1999Leloup et al. / LIMIT CYCLE MODELS FOR CIRCADIAN RHYTHMS Limit Cycle Models for Circadian Rhythms  

E-print Network

JOURNAL OF BIOLOGICAL RHYTHMS / December 1999Leloup et al. / LIMIT CYCLE MODELS FOR CIRCADIAN RHYTHMS Limit Cycle Models for Circadian Rhythms Based on Transcriptional Regulation in Drosophila models for circadian oscillations based on transcriptional regulation in Drosophila and Neurospora

Goldbeter, Albert

29

A proposal for robust temperature compensation of circadian rhythms  

PubMed Central

The internal circadian rhythms of cells and organisms coordinate their physiological properties to the prevailing 24-h cycle of light and dark on earth. The mechanisms generating circadian rhythms have four defining characteristics: they oscillate endogenously with period close to 24 h, entrain to external signals, suffer phase shifts by aberrant pulses of light or temperature, and compensate for changes in temperature over a range of 10°C or more. Most theoretical descriptions of circadian rhythms propose that the underlying mechanism generates a stable limit cycle oscillation (in constant darkness or dim light), because limit cycles quite naturally possess the first three defining properties of circadian rhythms. On the other hand, the period of a limit cycle oscillator is typically very sensitive to kinetic rate constants, which increase markedly with temperature. Temperature compensation is therefore not a general property of limit cycle oscillations but must be imposed by some delicate balance of temperature dependent effects. However, “delicate balances” are unlikely to be robust to mutations. On the other hand, if circadian rhythms arise from a mechanism that concentrates sensitivity into a few rate constants, then the “balancing act” is likely to be more robust and evolvable. We propose a switch-like mechanism for circadian rhythms that concentrates period sensitivity in just two parameters, by forcing the system to alternate between a stable steady state and a stable limit cycle. PMID:17229851

Hong, Christian I.; Conrad, Emery D.; Tyson, John J.

2007-01-01

30

Circadian Rhythms and Obesity in Mammals  

PubMed Central

Obesity has become a serious public health problem and a major risk factor for the development of illnesses, such as insulin resistance and hypertension. Attempts to understand the causes of obesity and develop new therapeutic strategies have mostly focused on caloric intake and energy expenditure. Recent studies have shown that the circadian clock controls energy homeostasis by regulating the circadian expression and/or activity of enzymes, hormones, and transport systems involved in metabolism. Moreover, disruption of circadian rhythms leads to obesity and metabolic disorders. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. Feeding regimens, such as restricted feeding (RF), calorie restriction (CR), and intermittent fasting (IF), provide a time cue and reset the circadian clock and lead to better health. In contrast, high-fat (HF) diet leads to disrupted circadian expression of metabolic factors and obesity. This paper focuses on circadian rhythms and their link to obesity. PMID:24527263

Froy, Oren

2012-01-01

31

Circadian rhythms and obesity in mammals.  

PubMed

Obesity has become a serious public health problem and a major risk factor for the development of illnesses, such as insulin resistance and hypertension. Attempts to understand the causes of obesity and develop new therapeutic strategies have mostly focused on caloric intake and energy expenditure. Recent studies have shown that the circadian clock controls energy homeostasis by regulating the circadian expression and/or activity of enzymes, hormones, and transport systems involved in metabolism. Moreover, disruption of circadian rhythms leads to obesity and metabolic disorders. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. Feeding regimens, such as restricted feeding (RF), calorie restriction (CR), and intermittent fasting (IF), provide a time cue and reset the circadian clock and lead to better health. In contrast, high-fat (HF) diet leads to disrupted circadian expression of metabolic factors and obesity. This paper focuses on circadian rhythms and their link to obesity. PMID:24527263

Froy, Oren

2012-01-01

32

Cell-autonomous circadian clock of hepatocytes drives rhythms in transcription and polyamine synthesis  

E-print Network

Cell-autonomous circadian clock of hepatocytes drives rhythms in transcription and polyamine. Kay, October 5, 2011 (sent for review August 3, 2011) The circadian clock generates daily rhythms profiling in Met murine hepatocytes (MMH)-D3, we identified over 1,000 transcripts that ex- hibit circadian

33

Circadian Rhythms: A Circadian Loop asSIRTs Itself  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required: Daily time keeping in many organisms depends on internal circadian clocks that temporally organize biological functions relative to each other as well as the environment. These clocks generate rhythms in physiology and behavior by using circuits of gene expression that are organized in negative-feedback loops. Two studies in this issue, by Nakahata et al. and Ramsey et al., propose the addition of a new negative-feedback loop to this circuitry that involves the metabolite nicotinamide adenine dinucleotide (NAD+) and the protein SIRTUIN1 (SIRT1). The new loop suggests connections between the circadian clock and SIRT1-dependent functions associated with cell survival, development, inflammation, and metabolism.

Herman Wijnen (University of Virginia; Department of Biology)

2009-05-01

34

Circadian Metabolic Rhythms in Obese Children  

Microsoft Academic Search

Obese children display constant hyperinsulinism and, frequently, hyperphagia. In animals, lesions of the hypothalamic system affect simultaneously the circadian rhythm of insulin secretion and of food intake. In this study, circadian metabolic rhythm was examined in obese and non-obese children, by two different protocols. (1) Oral glucose tolerance tests (OGTT) were carried out at 9 a.m. and 3 p.m. on

Jehan-François Desjeux; Catherine Gernez-Lestradet; Ingeborg Deschamps; Sylvine Machinot; Frédérique Rolland; Henri Lestradet

1982-01-01

35

[Circadian rhythm sleep disorders in psychiatric diseases].  

PubMed

Circadian rhythm sleep disorders are prevalent among psychiatric patients. This is most probable due to a close relationship between functional disturbances of the internal clock, sleep regulation and mental health. Mechanisms on molecular level of the circadian clock and neurotransmitter signalling are involved in the development of both disorders. Moreover, circadian disorders and psychiatric diseases favour each other by accessory symptoms such as stress or social isolation. Actimetry to objectively quantify the rest-activity cycle and salivary melatonin profiles as marker for the circadian phase help to diagnose circadian rhythm sleep disorders in psychiatric patients. Chronotherapeutics such as bright light therapy, dark therapy, melatonin administration, and wake therapy are used to synchronise and consolidate circadian rhythms and help in the treatment of depression and other psychiatric disorders, but are still neglected in medicine. More molecular to behavioural research is needed for the understanding of the development of circadian disorders and their relationship to psychiatric illnesses. This will help to boost the awareness and treatment of circadian rhythm sleep disorders in psychiatry. PMID:25377290

Bromundt, Vivien

2014-11-01

36

Circadian rhythms, athletic performance, and jet lag  

Microsoft Academic Search

Rapid air travel across several time zones exposes the traveller to a shift in his\\/her internal biological clock. The result is a transient desynchronisation of the circadian rhythm, called jet lag, lasting until the rhythm is rephased to the new environmental conditions. The most commonly experienced symptoms are sleep disorders, difficulties with concentrating, irritability, depression, fatigue, disorientation, loss of appetite,

R. Manfredini; F. Manfredini; C. Fersini; F. Conconi

1998-01-01

37

Modelling circadian rhythms of protein KaiA, KaiB and KaiC interactions in cyanobacteria  

E-print Network

Modelling circadian rhythms of protein KaiA, KaiB and KaiC interactions in cyanobacteria SHAO LI 100084, P. R. China Abstract Cyanobacteria are the simplest organisms known that exhibit circadian rhythms. The mechanism of circadian rhythm generation in cyanobacteria is different from eukaryotes. Based

Li, Shao

38

c-Jun N-TERMINAL KINASE INHIBITOR SP600125 MODULATES THE PERIOD OF MAMMALIAN CIRCADIAN RHYTHMS  

E-print Network

c-Jun N-TERMINAL KINASE INHIBITOR SP600125 MODULATES THE PERIOD OF MAMMALIAN CIRCADIAN RHYTHMS M/ULP UMR 7168, 67084, Strasbourg, France Abstract Circadian rhythms are endogenous cycles with periods close to, but not exactly equal to, 24 h. In mammals, circadian rhythms are generated

Harrington, Mary

39

Ageing and osteoarthritis: a circadian rhythm connection.  

PubMed

Osteoarthritis (OA) is the most common joint disease, affecting articular cartilage of the joints, with currently no cure. Age is a major risk factor for OA, but despite significant advances made in the OA research field, how ageing contributes to OA is still not well understood. In this review, we will focus on one particular aspect of chondrocyte biology, i.e., circadian rhythms. Disruptions to circadian clocks have been linked to various diseases. Our recent work demonstrates autonomous clocks in chondrocytes which regulate key pathways implicated in OA. The cartilage rhythm dampens with age and clock gene expression changes during the initiation stage of OA development in an experimental mouse OA model. Research into the molecular links between ageing, circadian clocks and OA may identify novel therapeutic routes for the prevention and management of OA, such as chronotherapy, or direct targeting of clock components/circadian rhythm. PMID:25078075

Gossan, Nicole; Boot-Handford, Ray; Meng, Qing-Jun

2015-04-01

40

Interactions Between Cognition and Circadian Rhythms: Attentional Demands Modify Circadian Entrainment  

E-print Network

Interactions Between Cognition and Circadian Rhythms: Attentional Demands Modify Circadian to changes in activity patterns during the rest of the circadian cycle. Here the authors demonstrate modification in the animals' activity throughout the entire circadian cycle. In particular, normally nocturnal

Lee, Theresa

41

Characterisation of circadian rhythms of various duckweeds.  

PubMed

The plant circadian clock controls various physiological phenomena that are important for adaptation to natural day-night cycles. Many components of the circadian clock have been identified in Arabidopsis thaliana, the model plant for molecular genetic studies. Recent studies revealed evolutionary conservation of clock components in green plants. Homologues of clock-related genes have been isolated from Lemna gibba and Lemna aequinoctialis, and it has been demonstrated that these homologues function in the clock system in a manner similar to their functioning in Arabidopsis. While clock components are widely conserved, circadian phenomena display diversity even within the Lemna genus. In order to survey the full extent of diversity in circadian rhythms among duckweed plants, we characterised the circadian rhythms of duckweed by employing a semi-transient bioluminescent reporter system. Using a particle bombardment method, circadian bioluminescent reporters were introduced into nine strains representing five duckweed species: Spirodela polyrhiza, Landoltia punctata, Lemna gibba, L. aequinoctialis and Wolffia columbiana. We then monitored luciferase (luc+) reporter activities driven by AtCCA1, ZmUBQ1 or CaMV35S promoters under entrainment and free-running conditions. Under entrainment, AtCCA1::luc+ showed similar diurnal rhythms in all strains. This suggests that the mechanism of biological timing under day-night cycles is conserved throughout the evolution of duckweeds. Under free-running conditions, we observed circadian rhythms of AtCCA1::luc+, ZmUBQ1::luc+ and CaMV35S::luc+. These circadian rhythms showed diversity in period length and sustainability, suggesting that circadian clock mechanisms are somewhat diversified among duckweeds. PMID:24942699

Muranaka, T; Okada, M; Yomo, J; Kubota, S; Oyama, T

2015-01-01

42

Circadian rhythms govern cardiac repolarization and arrhythmogenesis.  

PubMed

Sudden cardiac death exhibits diurnal variation in both acquired and hereditary forms of heart disease, but the molecular basis of this variation is unknown. A common mechanism that underlies susceptibility to ventricular arrhythmias is abnormalities in the duration (for example, short or long QT syndromes and heart failure) or pattern (for example, Brugada's syndrome) of myocardial repolarization. Here we provide molecular evidence that links circadian rhythms to vulnerability in ventricular arrhythmias in mice. Specifically, we show that cardiac ion-channel expression and QT-interval duration (an index of myocardial repolarization) exhibit endogenous circadian rhythmicity under the control of a clock-dependent oscillator, krüppel-like factor 15 (Klf15). Klf15 transcriptionally controls rhythmic expression of Kv channel-interacting protein 2 (KChIP2), a critical subunit required for generating the transient outward potassium current. Deficiency or excess of Klf15 causes loss of rhythmic QT variation, abnormal repolarization and enhanced susceptibility to ventricular arrhythmias. These findings identify circadian transcription of ion channels as a mechanism for cardiac arrhythmogenesis. PMID:22367544

Jeyaraj, Darwin; Haldar, Saptarsi M; Wan, Xiaoping; McCauley, Mark D; Ripperger, Jürgen A; Hu, Kun; Lu, Yuan; Eapen, Betty L; Sharma, Nikunj; Ficker, Eckhard; Cutler, Michael J; Gulick, James; Sanbe, Atsushi; Robbins, Jeffrey; Demolombe, Sophie; Kondratov, Roman V; Shea, Steven A; Albrecht, Urs; Wehrens, Xander H T; Rosenbaum, David S; Jain, Mukesh K

2012-03-01

43

Circadian rhythms govern cardiac repolarization and arrhythmogenesis  

PubMed Central

Sudden cardiac death exhibits diurnal variation in both acquired and hereditary forms of heart disease 1, 2, but the molecular basis is unknown. A common mechanism that underlies susceptibility to ventricular arrhythmias is abnormalities in the duration (e.g. short or long QT syndromes, heart failure) 3-5 or pattern (e.g. Brugada syndrome) 6 of myocardial repolarization. Here we provide the first molecular evidence that links circadian rhythms to vulnerability in ventricular arrhythmias in mice. Specifically, we show that cardiac ion channel expression and QT interval duration (an index of myocardial repolarization) exhibit endogenous circadian rhythmicity under the control of a novel clock-dependent oscillator, Krüppel-like factor 15 (Klf15). Klf15 transcriptionally controls rhythmic expression of KChIP2, a critical subunit required for generating the transient outward potassium current (Ito). 7 Deficiency or excess of Klf15 causes loss of rhythmic QT variation, abnormal repolarization and enhanced susceptibility to ventricular arrhythmias. In sum, these findings identify circadian transcription of ion channels as a novel mechanism for cardiac arrhythmogenesis. PMID:22367544

Jeyaraj, Darwin; Haldar, Saptarsi M.; Wan, Xiaoping; McCauley, Mark D.; Ripperger, Jürgen A.; Hu, Kun; Lu, Yuan; Eapen, Betty L.; Sharma, Nikunj; Ficker, Eckhard; Cutler, Michael J.; Gulick, James; Sanbe, Atsushi; Robbins, Jeffrey; Demolombe, Sophie; Kondratov, Roman V.; Shea, Steven A.; Albrecht, Urs; Wehrens, Xander H.T.; Rosenbaum, David S.; Jain, Mukesh K.

2012-01-01

44

Circadian rhythms of women with fibromyalgia  

NASA Technical Reports Server (NTRS)

Fibromyalgia syndrome is a chronic and debilitating disorder characterized by widespread nonarticular musculoskeletal pain whose etiology is unknown. Many of the symptoms of this syndrome, including difficulty sleeping, fatigue, malaise, myalgias, gastrointestinal complaints, and decreased cognitive function, are similar to those observed in individuals whose circadian pacemaker is abnormally aligned with their sleep-wake schedule or with local environmental time. Abnormalities in melatonin and cortisol, two hormones whose secretion is strongly influenced by the circadian pacemaker, have been reported in women with fibromyalgia. We studied the circadian rhythms of 10 women with fibromyalgia and 12 control healthy women. The protocol controlled factors known to affect markers of the circadian system, including light levels, posture, sleep-wake state, meals, and activity. The timing of the events in the protocol were calculated relative to the habitual sleep-wake schedule of each individual subject. Under these conditions, we found no significant difference between the women with fibromyalgia and control women in the circadian amplitude or phase of rhythms of melatonin, cortisol, and core body temperature. The average circadian phases expressed in hours posthabitual bedtime for women with and without fibromyalgia were 3:43 +/- 0:19 and 3:46 +/- 0:13, respectively, for melatonin; 10:13 +/- 0:23 and 10:32 +/- 0:20, respectively for cortisol; and 5:19 +/- 0:19 and 4:57 +/- 0:33, respectively, for core body temperature phases. Both groups of women had similar circadian rhythms in self-reported alertness. Although pain and stiffness were significantly increased in women with fibromyalgia compared with healthy women, there were no circadian rhythms in either parameter. We suggest that abnormalities in circadian rhythmicity are not a primary cause of fibromyalgia or its symptoms.

Klerman, E. B.; Goldenberg, D. L.; Brown, E. N.; Maliszewski, A. M.; Adler, G. K.

2001-01-01

45

Role of Circadian Rhythms in Potassium Homeostasis  

PubMed Central

It has been known for decades that urinary potassium excretion varies with a circadian pattern. In this review, we consider the historical evidence for this phenomenon and present an overview of recent developments in the field. Extensive evidence from the latter part of the last century clearly demonstrates that circadian potassium excretion does not depend on endogenous aldosterone. Of note is the recent discovery that the expression of several renal potassium transporters varies with a circadian pattern that appears to be consistent with substantial clinical data regarding daily fluctuations in urinary potassium levels. We propose the circadian clock mechanism as a key regulator of renal potassium transporters, and consequently renal potassium excretion. Further investigation into the mechanism of regulation of renal potassium transport by the circadian clock is warranted in order to increase our understanding of the clinical relevance of circadian rhythms to potassium homeostasis. PMID:23953800

Gumz, Michelle L.; Rabinowitz, Lawrence

2013-01-01

46

Circadian Synchrony in Networks of Protein Rhythm Driven Neurons  

E-print Network

Circadian Synchrony in Networks of Protein Rhythm Driven Neurons WILLIAM S. BUSH AND HAVA T; suprachiasmatic nucleus; protein expression; circadian rhythms INTRODUCTION S yncronicity has been examined M P L E X I T Y 67 DOI 10.1002/cplx.20145 #12;circadian rhythms, such as the sleep­wake cycle

Siegelmann , Hava T

47

Circadian rhythms in Macaca mulatta monkeys during Bion 11 flight  

NASA Technical Reports Server (NTRS)

Circadian rhythms of primate brain temperature, head and ankle skin temperature, motor activity, and heart rate were studied during spaceflight and on the ground. In space, the circadian rhythms of all the parameters were synchronized with diurnal Zeitgebers. However, in space the brain temperature rhythm showed a significantly more delayed phase angle, which may be ascribed to an increase of the endogenous circadian period.

Alpatov, A. M.; Hoban-Higgins, T. M.; Klimovitsky, V. Y.; Tumurova, E. G.; Fuller, C. A.

2000-01-01

48

Circadian rhythms of performance: new trends  

NASA Technical Reports Server (NTRS)

This brief review is concerned with how human performance efficiency changes as a function of time of day. It presents an overview of some of the research paradigms and conceptual models that have been used to investigate circadian performance rhythms. The influence of homeostatic and circadian processes on performance regulation is discussed. The review also briefly presents recent mathematical models of alertness that have been used to predict cognitive performance. Related topics such as interindividual differences and the postlunch dip are presented.

Carrier, J.; Monk, T. H.

2000-01-01

49

Circadian rhythm entrainment in flies and mammals  

Microsoft Academic Search

Circadian rhythms are a fundamental adaptation of living cells to the daily and seasonal fluctuation in light and temperature.\\u000a Circadian oscillations persist in constant conditions; however, they are also phase-adjusted (entrained) by day-night cycles.\\u000a It is this entrainability that provides for the proper phasing of the program, to the sequence of external changes that it\\u000a has evolved to exploit. Synchronization

Rachel Ben-Shlomo; Charalambos P. Kyriacou

2002-01-01

50

Circadian rhythm of cortisol and estradiol in healthy women  

Microsoft Academic Search

Daily variation in human processes and behaviors has been identified for centuries. Study of these circadian rhythms demonstrates their role in human health. Sickness behaviors include alterations in affect, sleep quality and energy. The study of the relationship between circadian rhythms has been limited to isolated rhythms. The role of temporal relationships among rhythms has received little attention. Sickness behaviors

Karyn G Butler

2011-01-01

51

Circadian Rhythms and Psychiatric Illness  

PubMed Central

Purpose of review The present review provides a conceptual introduction to sleep and circadian research in psychiatric illness, and discusses recent experimental and intervention findings in this area. Recent Findings In this review, studies published since January 2011 on circadian disturbance and psychiatric illness have been summarized. Summary Exciting new results have increasingly utilized objective and validated instruments to measure the circadian system in experimental studies. Since 2011, treatment research has still predominantly utilized self-report measures as outcome variables. However, research in the treatment domain for sleep/circadian disturbances comorbid with psychiatric illness has advanced the field in its work to broaden the validation of existing sleep treatments to additional patient populations with comorbid sleep/circadian disruptions, address how to increase access to and affordability of treatment for sleep and circadian dysfunction for patients with psychiatric disorders, and how to combine psychosocial treatments with psychopharmacology to optimize treatment outcomes. PMID:24060916

Asarnow, Lauren D.; Soehner, Adriane M.; Harvey, Allison G.

2014-01-01

52

Sleep and circadian rhythm disruption in psychiatric and neurodegenerative disease  

Microsoft Academic Search

Sleep and circadian rhythm disruption are frequently observed in patients with psychiatric disorders and neurodegenerative disease. The abnormal sleep that is experienced by these patients is largely assumed to be the product of medication or some other influence that is not well defined. However, normal brain function and the generation of sleep are linked by common neurotransmitter systems and regulatory

Katharina Wulff; Silvia Gatti; Joseph G. Wettstein; Russell G. Foster

2010-01-01

53

A circadian rhythm of conidiation in Neurospora crassa (L-12)  

NASA Technical Reports Server (NTRS)

Two fungi growth chambers containing six growth tubes each are used in this experiment. One chamber is for the space experiment; the other is for the simultaneous ground control experiment. The hyphae of Neurospora crassa band A mutant are inoculated at one end of each tube. Both the chambers are kept at 3 C plus or minus 1.5 C to stop hyphae growth until the Spacelab is activated. After the activation, each chamber is transferred simultaneously to the Spacelab and a phytotron in KSC and kept in continuous light at the same temperature. After about 24 hours of light exposure, each chamber is inserted into a growth chamber bag to keep it in constant darkness. The circadian rhythm of conidiation is initiated by this light to dark transition. After the dark incubation for 5 days at room temperature, both the growth chambers are kept at 3 C plus or minus 1.5 C to stop growth of the hyphae. After the space shuttle lands, both conidiation patterns are compared and analyzed. It has been known that numerous physiological phenomena show circadian rhythms. They are characterized by the fact that the oscillation can persist under constant conditions of light and temperature. Therefore, it has been accepted by most investigators that the generation mechanism of the circadian rhythm is endogeneous. However, one cannot reject the possibility that these rhythms are caused by some geophysical exogeneous factor having a 24-hour period, such as atmospheric pressure, gravity, or electromagnetic radiation. We use Neurospora crassa band A mutual which shows an obvious circadian rhythm in its spore-forming (conidiation) on the ground, and we intend to attempt the conidation of this mutant in the Spacelab where 24-hour periodicity is severely attenuated and to elucidate the effect of the geophysical exogeneous factor in the generation mechanism of the circadian rhythm.

Miyoshi, Yashuhiro

1993-01-01

54

Procedures for numerical analysis of circadian rhythms  

PubMed Central

This article reviews various procedures used in the analysis of circadian rhythms at the populational, organismal, cellular and molecular levels. The procedures range from visual inspection of time plots and actograms to several mathematical methods of time series analysis. Computational steps are described in some detail, and additional bibliographic resources and computer programs are listed. PMID:23710111

REFINETTI, ROBERTO; LISSEN, GERMAINE CORNÉ; HALBERG, FRANZ

2010-01-01

55

Circadian Rhythms in Animals: A Canonical Connections Map  

NSDL National Science Digital Library

Circadian rhythms are near-24-hour endogenous rhythms of behavior and physiology that are a nearly universal feature of eukaryotic life. Genetic and biochemical experiments over the past decade have allowed the construction of a viable working model for the molecular mechanisms underlying circadian rhythm generation in animals. The basic mechanism consists of two intertwined transcription-translation negative feedback loops. One loop--the "positive loop"--controls the rhythmic expression of a well-conserved Per-Arnt-Sim (PAS)-domain-containing positive transcription factor (Clock in Drosophila, and BMAL1, which is also known as MOP3, in the mouse). The second loop--the "negative loop"--controls the expression of another PAS-domain protein (the repressor Period), as well as species-specific repressors (Timeless in Drosophila and Cryptochrome in mice). The loops are intertwined because Period and its binding partners directly repress transcription mediated by Clock and its binding partners (Cycle in Drosophila and BMAL1 in the mouse), whereas Clock:Cycle (or CLOCK:BMAL1) drives the transcription of period and the other repressors, as well as that of repressors of Clock or Bmal1 transcriptional expression. Other factors, including conserved kinases such as Casein kinase I ε (CkIε), have essential functions in the timekeeping mechanism. Remarkably, this mechanism appears to be fundamentally conserved between Drosophila and mammalian circadian clocks. This Canonical Connections Map Pathway describes the basic mechanism underlying circadian signaling, whereas the accompanying specific Pathway Maps for Drosophila and murine circadian mechanisms describe the individual known components of the circadian clock and their mutual interactions. Science Viewpoint R. N. Van Gelder, E. D. Herzog, W. J. Schwartz, P. H. Taghert, Circadian rhythms: In the loop at last. Science 300, 1534-1535 (2003). [Abstract] [Full Text

Russell N. Van Gelder (Washington University Medical School; Department of Ophthalmology and Visual Sciences and Department of Molecular Biology and Pharmacology REV)

2003-08-05

56

A novel animal model linking adiposity to altered circadian rhythms  

Technology Transfer Automated Retrieval System (TEKTRAN)

Researchers have provided evidence for a link between obesity and altered circadian rhythms (e.g., shift work, disrupted sleep), but the mechanism for this association is still unknown. Adipocytes possess an intrinsic circadian clock, and circadian rhythms in adipocytokines and adipose tissue metab...

57

Circadian rhythms and molecular noise Didier Gonze and Albert Goldbeter  

E-print Network

Circadian rhythms and molecular noise Didier Gonze and Albert Goldbeter Faculté des Sciences; accepted 17 May 2006; published online 30 June 2006 Circadian rhythms, characterized by a period of about. The core molecular mechanism responsible for circadian oscillations relies on the negative regulation

Goldbeter, Albert

58

Modeling the molecular regulatory mechanism of circadian rhythms  

E-print Network

Modeling the molecular regulatory mechanism of circadian rhythms in Drosophila Jean mechanism of circadian rhythms in Drosoph- ila, theoretical models closely related to experimental observations can be considered for the regulatory mechanism of the circadian clock in this organism. Mod- eling

Goldbeter, Albert

59

Gender differences in the circadian rhythms of rhesus monkeys  

Microsoft Academic Search

Studies investigating gender differences in human circadian rhythms report equivocal results. In addition, many of these studies have been limited to examination of one circadian variable. This study examined gender differences in circadian rhythms of multiple physiological variables of rhesus monkeys under highly controlled conditions. Under general anesthesia, eight female and seven male rhesus were implanted with a biotelemetry transmitter

Laura K. Barger; Tana M. Hoban-Higgins; Charles A. Fuller

2010-01-01

60

Environmental synchronizers of squirrel monkey circadian rhythms  

NASA Technical Reports Server (NTRS)

Various temporal signals in the environment were tested to determine if they could synchronize the circadian timing system of the squirrel monkey (Saimiri sciureus). The influence of cycles of light and dark, eating and fasting, water availability and deprivation, warm and cool temperature, sound and quiet, and social interaction and isolation on the drinking and activity rhythms of unrestrained monkeys was examined. In the absence of other time cues, 24-hr cycles of each of these potential synchronizers were applied for up to 3 wk, and the periods of the monkey's circadian rhythms were examined. Only light-dark cycles and cycles of food availability were shown to be entraining agents, since they were effective in determining the period and phase of the rhythmic variables. In the presence of each of the other environmental cycles, the monkey's circadian rhythms exhibited free-running periods which were significantly different from 24 hr with all possible phase relationships between the rhythms and the environmental cycles being examined.

Sulzman, F. M.; Fuller, C. A.; Moore-Ede, M. C.

1977-01-01

61

Endogenous circadian rhythm in human motor activity uncoupled from circadian influences  

E-print Network

Endogenous circadian rhythm in human motor activity uncoupled from circadian influences on cardiac. Eugene Stanley, October 31, 2007 (sent for review September 27, 2007) The endogenous circadian pacemaker found that a scaling index of cardiac vulnerability has an endogenous circadian peak at the circadian

Stanley, H. Eugene

62

Circadian rhythm asynchrony in man during hypokinesis.  

NASA Technical Reports Server (NTRS)

Posture and exercise were investigated as synchronizers of certain physiologic rhythms in eight healthy male subjects in a defined environment. Four subjects exercised during bed rest. Body temperature (BT), heart rate, plasma thyroid hormone, and plasma steroid data were obtained from the subjects for a 6-day ambulatory equilibration period before bed rest, 56 days of bed rest, and a 10-day recovery period after bed rest. The results indicate that the mechanism regulating the circadian rhythmicity of the cardiovascular system is rigorously controlled and independent of the endocrine system, while the BT rhythm is more closely aligned to the endocrine system.

Winget, C. M.; Vernikos-Danellis, J.; Cronin, S. E.; Leach, C. S.; Rambaut, P. C.; Mack, P. B.

1972-01-01

63

Circadian rhythms, athletic performance, and jet lag  

PubMed Central

Rapid air travel across several time zones exposes the traveller to a shift in his/her internal biological clock. The result is a transient desynchronisation of the circadian rhythm, called jet lag, lasting until the rhythm is rephased to the new environmental conditions. The most commonly experienced symptoms are sleep disorders, difficulties with concentrating, irritability, depression, fatigue, disorientation, loss of appetite, and gastrointestinal disturbance. Apart from the decrements in mental and physical performance directly consequent on such symptoms, competitive athletes are also exposed to the additional negative consequences of a shift from the optimal circadian window of performance. A brief summary of the possible negative effects of jet lag on athletic performance and potentially alleviating strategies is given. ????? PMID:9631214

Manfredini, R.; Manfredini, F.; Fersini, C.; Conconi, F.

1998-01-01

64

Circadian rhythm and cell population growth  

E-print Network

Molecular circadian clocks, that are found in all nucleated cells of mammals, are known to dictate rhythms of approximately 24 hours (circa diem) to many physiological processes. This includes metabolism (e.g., temperature, hormonal blood levels) and cell proliferation. It has been observed in tumor-bearing laboratory rodents that a severe disruption of these physiological rhythms results in accelerated tumor growth. The question of accurately representing the control exerted by circadian clocks on healthy and tumour tissue proliferation to explain this phenomenon has given rise to mathematical developments, which we review. The main goal of these previous works was to examine the influence of a periodic control on the cell division cycle in physiologically structured cell populations, comparing the effects of periodic control with no control, and of different periodic controls between them. We state here a general convexity result that may give a theoretical justification to the concept of cancer chronothera...

Clairambault, Jean; Lepoutre, Thomas

2010-01-01

65

Circadian rhythms and sleep in human aging.  

PubMed

This issue of Chronobiology International is dedicated to the age-related changes in circadian rhythms as they occur in humans. It seems timely to give an overview of the knowledge and hypotheses on these changes now that we enter a century in which the number and percentage of elderly in the population will be unprecedented. Although we should take care not to follow the current tendency to think of old age as a disease--ignoring the fine aspects of being old--there is definitely an age-related increase in the risk of a number of conditions that are at least uncomfortable. Circadian rhythms have been attributed adaptive values that usually go unnoticed, but can surface painfully clear when derangements occur. Alterations in the regulation of circadian rhythms are thought to contribute to the symptoms of a number of conditions for which the risk is increased in old age (e.g., sleep disturbances, dementia, and depression). A multidisciplinary approach to investigate the mechanisms of age-related changes in circadian regulation eventually may result in treatment strategies that will improve the quality of life of the growing number of elderly. Although diverse topics are addressed in this issue, the possible mechanisms by which a deranged circadian timing system may be involved in sleep disturbances receives the most attention. This seems appropriate in view of the numerous studies that have addressed this relation in the last decade and also because of the high frequency and strong impact of sleep disturbances in the elderly. This introduction to the special issue first briefly addresses the impact of disturbed sleep in the elderly to show that the development of therapeutic methods other than the currently available pharmacological treatments should be given high priority. I believe that chronobiological insights may play an important role in the development of rational therapeutical methods. PMID:10841205

Van Someren, E J

2000-05-01

66

Circadian rhythms in lizards: phase response curve for melatonin.  

PubMed

Single biweekly injections of melatonin were administered to lizards (Sceloporus occidentalis) free-running (exhibiting their endogenous circadian activity rhythm) in constant dim illumination. The injections caused phase shifts in the activity rhythm whose magnitude and direction were a function of the time of the melatonin injections, relative to activity onsets. Plotting the direction and amount of phase shift versus the time (phase) at which the injection was given generates a phase-response curve (PRC). The PRC shows that injections administered between midsubjective day and early subjective night (6-15 hr after activity onset) elicit phase advances in the activity rhythm, whereas injections given at other phases of the activity cycle induce phase delays. The existence of a PRC for melatonin suggests that the daily endogenous rhythm of melatonin (i.e., of pineal origin) may be involved in phasing, or entraining, the circadian system of lizards. The shape of the PRC also allows predictions as to the effects of continuous exogenous melatonin administration on the period of free-running activity rhythms as well as on the mechanism of entrainment of activity rhythms to daily melatonin injections. PMID:3723331

Underwood, H

1986-01-01

67

INTRINSIC CIRCADIAN RHYTHMS IN THE CARDIOMYOCYTE  

Technology Transfer Automated Retrieval System (TEKTRAN)

The cardiomyocyte possesses a fully functional circadian clock. Circadian clocks are a set of proteins that generate self-sustained transcriptional positive and negative feedback loops with a free-running period of 24 hours. These intracellular molecular mechanisms confer the selective advantage of ...

68

Temperature compensation and entrainment in circadian rhythms  

NASA Astrophysics Data System (ADS)

To anticipate daily variations in the environment and coordinate biological activities into a daily cycle many organisms possess a circadian clock. In the absence of external time cues the circadian rhythm persists with a period of approximately 24?h. The clock phase can be shifted by single pulses of light, darkness, chemicals, or temperature and this allows entrainment of the clock to exactly 24 h by cycles of these zeitgebers. On the other hand, the period of the circadian rhythm is kept relatively constant within a physiological range of constant temperatures, which means that the oscillator is temperature compensated. The mechanisms behind temperature compensation and temperature entrainment are not fully understood, neither biochemically nor mathematically. Here, we theoretically investigate the interplay of temperature compensation and entrainment in general oscillatory systems. We first give an analytical treatment for small temperature shifts and derive that every temperature-compensated oscillator is entrainable to external small-amplitude temperature cycles. Temperature compensation ensures that this entrainment region is always centered at the endogenous period regardless of possible seasonal temperature differences. Moreover, for small temperature cycles the entrainment region of the oscillator is potentially larger for rectangular pulses. For large temperature shifts we numerically analyze different circadian clock models proposed in the literature with respect to these properties. We observe that for such large temperature shifts sinusoidal or gradual temperature cycles allow a larger entrainment region than rectangular cycles.

Bodenstein, C.; Heiland, I.; Schuster, S.

2012-06-01

69

Dissecting circadian performance rhythms: implications for shiftwork.  

PubMed

Safety on shift systems will depend, at least in part, on the adjustment of shiftworkers' circadian (c.24h) rhythms in performance capabilities which will in turn depend on their underlying control. In the present study three volunteers lived on a 30h 'day' and performed a range of tasks every 2h (while awake) to allow estimates of the relative magnitude of the endogenous (body clock) and exogenous (masking) components of their rhythms to be made. Performance rhythms were found to differ considerably in this respect with, for example, speed on a 4-choice serial reaction time task appearing to be largely endogenously determined while that on a 5-target Sternberg task was more dependent on exogenous (i.e., 30h) factors. This implies that performance measures may adjust at very different rates to one another to night work, and hence that the optimal form of shift system may vary according to the precise demands of the shiftworker's task. PMID:8440223

Folkard, S; Totterdell, P; Minors, D; Waterhouse, J

1993-01-01

70

N-nitrosomelatonin enhances photic synchronization of mammalian circadian rhythms.  

PubMed

Most physiological processes in mammals are synchronized to the daily light:dark cycle by a circadian clock located in the hypothalamic suprachiasmatic nucleus. Signal transduction of light-induced phase advances of the clock is mediated through a neuronal nitric oxide synthase-guanilyl cyclase pathway. We have employed a novel nitric oxide-donor, N-nitrosomelatonin, to enhance the photic synchronization of circadian rhythms in hamsters. The intraperitoneal administration of this drug before a sub-saturating light pulse at circadian time 18 generated a twofold increase of locomotor rhythm phase-advances, having no effect over saturating light pulses. This potentiation was also obtained even when inhibiting suprachiasmatic nitric oxide synthase activity. However, N-nitrosomelatonin had no effect on light-induced phase delays at circadian time 14. The photic-enhancing effects were correlated with an increased suprachiasmatic immunoreactivity of FBJ murine osteosarcoma viral oncogene and period1. Moreover, in vivo nitric oxide release by N-nitrosomelatonin was verified by measuring nitrate and nitrite levels in suprachiasmatic nuclei homogenates. The compound also accelerated resynchronization to an abrupt 6-h advance in the light:dark cycle (but not resynchronization to a 6-h delay). Here, we demonstrate the chronobiotic properties of N-nitrosomelatonin, emphasizing the importance of nitric oxide-mediated transduction for circadian phase advances. PMID:24261470

Baidanoff, Fernando M; Plano, Santiago A; Doctorovich, Fabio; Suárez, Sebastián A; Golombek, Diego A; Chiesa, Juan J

2014-04-01

71

Circadian Rhythms in the Mouse: A Connections Map  

NSDL National Science Digital Library

Genetic and biochemical experiments over the past decade have facilitated the construction of a viable working model for the molecular mechanisms that generate the circadian rhythm in Mus musculus. The basic mechanism consists of two intertwined transcription-translation negative feedback loops. One, the "positive loop," controls the rhythmic expression of a Per-Arnt-Sim (PAS)-domain-containing positive transcription factor, BMAL1 (also called MOP3). The other, the "negative loop," controls the transcription of mPeriod 1 and 2 and mCryptochrome 1 and 2, two families of genes that encode repressor proteins. The loops are intertwined because the proteins mPeriod and mCryptochrome directly repress transcription mediated by the CLOCK:BMAL1 heterodimer, whereas CLOCK:BMAL1 drives transcription of the mPeriod and mCryptochrome genes, as well as that of Rev-erb-alpha, a repressor of Bmal1 expression. Mutations, including the tau mutation in hamsters [encoding Casein kinase I ε (CkIε)], have identified essential functions for other proteins in the timekeeping mechanism. The master pacemaker for circadian rhythms in mice is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Light cycles can synchronize molecular rhythms in the SCN by stimulating the release of glutamate and the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) from melanopsin-containing retinal ganglion cells. This results in increased transcription of mPeriod genes and a shift in the phase of the clock. This Pathway Map of the murine circadian mechanism describes the individual known components of the mouse circadian clock and their mutual interactions. Science Viewpoint R. N. Van Gelder, E. D. Herzog, W. J. Schwartz, P. H. Taghert, Circadian rhythms: In the loop at last. Science 300, 1534-1535 (2003). [Abstract] [Full Text

Russell N. Van Gelder (Washington University Medical School; Department of Molecular Biology and Pharmacology REV)

2003-08-05

72

Circadian rhythms in healthy aging--effects downstream from the pacemaker  

NASA Technical Reports Server (NTRS)

Using both previously published findings and entirely new data, we present evidence in support of the argument that the circadian dysfunction of advancing age in the healthy human is primarily one of failing to transduce the circadian signal from the circadian timing system (CTS) to rhythms "downstream" from the pacemaker rather than one of failing to generate the circadian signal itself. Two downstream rhythms are considered: subjective alertness and objective performance. For subjective alertness, we show that in both normal nychthemeral (24 h routine, sleeping at night) and unmasking (36 h of constant wakeful bed rest) conditions, advancing age, especially in men, leads to flattening of subjective alertness rhythms, even when circadian temperature rhythms are relatively robust. For objective performance, an unmasking experiment involving manual dexterity, visual search, and visual vigilance tasks was used to demonstrate that the relationship between temperature and performance is strong in the young, but not in older subjects (and especially not in older men).

Monk, T. H.; Kupfer, D. J.

2000-01-01

73

Circadian rhythms, sleep, and performance in space  

NASA Technical Reports Server (NTRS)

Maintaining optimal alertness and neurobehavioral functioning during space operations is critical to enable the National Aeronautics and Space Administration's (NASA's) vision "to extend humanity's reach to the Moon, Mars and beyond" to become a reality. Field data have demonstrated that sleep times and performance of crewmembers can be compromised by extended duty days, irregular work schedules, high workload, and varying environmental factors. This paper documents evidence of significant sleep loss and disruption of circadian rhythms in astronauts and associated performance decrements during several space missions, which demonstrates the need to develop effective countermeasures. Both sleep and circadian disruptions have been identified in the Behavioral Health and Performance (BH&P) area and the Advanced Human Support Technology (AHST) area of NASA's Bioastronautics Critical Path Roadmap. Such disruptions could have serious consequences on the effectiveness, health, and safety of astronaut crews, thus reducing the safety margin and increasing the chances of an accident or incident. These decrements oftentimes can be difficult to detect and counter effectively in restrictive operational environments. NASA is focusing research on the development of optimal sleep/wake schedules and countermeasure timing and application to help mitigate the cumulative effects of sleep and circadian disruption and enhance operational performance. Investing research in humans is one of NASA's building blocks that will allow for both short- and long-duration space missions and help NASA in developing approaches to manage and overcome the human limitations of space travel. In addition to reviewing the current state of knowledge concerning sleep and circadian disruptions during space operations, this paper provides an overview of NASA's broad research goals. Also, NASA-funded research, designed to evaluate the relationships between sleep quality, circadian rhythm stability, and performance proficiency in both ground-based simulations and space mission studies, as described in the 2003 NASA Task Book, will be reviewed.

Mallis, M. M.; DeRoshia, C. W.

2005-01-01

74

Vasoactive Intestinal Polypeptide Mediates Circadian Rhythms in Mammalian Olfactory Bulb and Olfaction  

PubMed Central

Accumulating evidence suggests that the olfactory bulbs (OBs) function as an independent circadian system regulating daily rhythms in olfactory performance. However, the cells and signals in the olfactory system that generate and coordinate these circadian rhythms are unknown. Using real-time imaging of gene expression, we found that the isolated olfactory epithelium and OB, but not the piriform cortex, express similar, sustained circadian rhythms in PERIOD2 (PER2). In vivo, PER2 expression in the OB of mice is circadian, approximately doubling with a peak around subjective dusk. Furthermore, mice exhibit circadian rhythms in odor detection performance with a peak at approximately subjective dusk. We also found that circadian rhythms in gene expression and odor detection performance require vasoactive intestinal polypeptide (VIP) or its receptor VPAC2R. VIP is expressed, in a circadian manner, in interneurons in the external plexiform and periglomerular layers, whereas VPAC2R is expressed in mitral and external tufted cells in the OB. Together, these results indicate that VIP signaling modulates the output from the OB to maintain circadian rhythms in the mammalian olfactory system. PMID:24760863

Miller, Jae-eun Kang; Granados-Fuentes, Daniel; Wang, Thomas; Marpegan, Luciano; Holy, Timothy E.

2014-01-01

75

Drosophila Circadian Rhythms: Stability Robustness Analysis and Model Reduction  

E-print Network

Drosophila Circadian Rhythms: Stability Robustness Analysis and Model Reduction Jorge M. Gonc investigates two models of circadian rhythms in Drosophila: one by Gonze et al. and a more generic model by Vilar et al. that describes the biological clock in Drosophila as well as other organisms. For both

Gonçalves, Jorge

76

Circadian Activity Rhythms, Time Urgency, and Achievement Concerns.  

ERIC Educational Resources Information Center

Many physiological and psychological processes fluctuate throughout the day in fairly stable, rhythmic patterns. The relationship between individual differences in circadian activity rhythms and a sense of time urgency were explored as well as a number of achievement-related variables. Undergraduates (N=308), whose circadian activity rhythms were…

Watts, Barbara L.

77

A Circadian Rhythm Regulating Hyphal Melanization in Cercospora Kikuchii  

Technology Transfer Automated Retrieval System (TEKTRAN)

Circadian rhythms, biochemical or developmental processes with a period length of approximately 24 hours, are thoroughly documented in plants and animals. However, virtually all of what is currently known about circadian rhythms in fungi is derived from the model fungus, Neurospora crassa, including...

78

Robust and tunable circadian rhythms from differentially sensitive catalytic domains  

E-print Network

Robust and tunable circadian rhythms from differentially sensitive catalytic domains Connie Phonga, Dallas, TX, and approved November 27, 2012 (received for review July 15, 2012) Circadian clocks, in a reconstituted circadian system from cyanobacteria, these con- flicting requirements are satisfied by distinct

Gardel, Margaret

79

Circadian rhythm and cell population growth June 17, 2010  

E-print Network

Circadian rhythm and cell population growth June 17, 2010 Jean Clairambault 1 , 2 , St´ephane Gaubert 3 , 4 and Thomas Lepoutre 1 , 5 Abstract Molecular circadian clocks, that are found in all exerted by circadian clocks on healthy and tumour tissue proliferation to explain this phenomenon has

80

Circadian rhythms in olfactory responses of Drosophila melanogaster  

Microsoft Academic Search

The core mechanism of circadian timekeeping in arthropods and vertebrates consists of feedback loops involving several clock genes, including period (per) and timeless (tim),. In the fruitfly Drosophila, circadian oscillations in per expression occur in chemosensory cells of the antennae, even when the antennae are excised and maintained in isolated organ culture. Here we demonstrate a robust circadian rhythm in

Balaji Krishnan; Stuart E. Dryer; Paul E. Hardin

1999-01-01

81

[Circadian rhythm disruption and human development].  

PubMed

Ontogenetic developments of rest-activity, sleep-wakefulness, temperature and several hormone rhythms in humans were reviewed. The reported effects of environment on these alterations were also summarized. Then, disorders or conditions which often encounter during early stage of life and reveal circadian rhythm disruptions were described. These disorders or conditions included severe brain damage, visual disturbance, developmental disorders(autistic spectrum disorder and attention deficit/hyperactivity disorder), Rett syndrome, Angelman syndrome, Smith-Magenis syndrome, epilepsy, Yonaki, and inadequate sleep hygiene. Finally, it was emphasized that we should pay special attention on the development of youngsters who showed sleep disturbance during early stage of life with special reference to the later occurrence of developmental disorders. PMID:24437259

Kohyama, Jun

2013-12-01

82

Circadian Rhythms, Aging, and Life Span in Mammals  

NSDL National Science Digital Library

Resetting the circadian clock leads to well being and increased life span, whereas clock disruption is associated with aging and morbidity. Increased longevity and improved health can be achieved by different feeding regimens that reset circadian rhythms and may lead to better synchrony in metabolism and physiology. This review focuses on recent findings concerning the relationships between circadian rhythms, aging attenuation, and life-span extension in mammals.

Oren Froy (The Hebrew University of Jerusalem Institute of Biochemistry, Food Science and Nutrition)

2011-08-01

83

Characterization of neurospora circadian rhythms in space  

NASA Technical Reports Server (NTRS)

To determine whether the circadian rhythm of conidiation in neurospora crassa is endogenously derived or is driven by some geophysical time cue, an experiment was conducted on space shuttle flight STS-9, where inoculated race tubes were exposed to the microgravity environment of space. The results demonstated that the rhythm can persist in space. However, there were several minor alterations noted; an increase in the period of the oscillation and the variability of the growth rate and a diminished rhythm amplitude, which eventually damped out in 25% of the flight tubes. On day seven of the flight, the tubes were exposed to light while their growth fronts were marked. It appears that some aspects of this marking process reinstated a robust rhythm in all the tubes which continued throughout the remainder of the flight. It was hypothesized that the damping found prior to the marking procedure on STS-9 may have been a result of the hypergravity pulse of launch and not due to the microgravity of the orbital lab; furthermore, that the marking procedure, by exposing the samples to light, had reinstated rhythmicity. To test this, an investigation was conducted into the effects of acute and chronic exposure to hypergravity.

Ferraro, James S.

1987-01-01

84

Circadian temperature rhythms of older people  

NASA Technical Reports Server (NTRS)

This collection of studies had the aim of exploring whether older (77+ years) men and women have circadian body temperature rhythms different from those of younger adults. A total of 20 older men and 28 older women were compared with either 22 young men or 14 middle-aged men in four protocols; all but the first protocol using a subset of the sample. The four protocols were: 1) 24 h, and 2) 72 h data collections on a normal laboratory routine (sleeping at night); 3) between 36 h and 153 h of field data collection at home; and 4) 36 h of a constant conditions routine (wakeful bedrest under temporal isolation) in the laboratory. There was some evidence for an age-related phase advance in temperature rhythm, especially for the older men on a normal routine, though this was not present in the constant conditions protocol, where 5 of the older subjects showed major delays in the timing of the body temperature trough (10:00 or later). There was no statistically significant evidence from any of the protocols that older subjects generally had lower temperature rhythm amplitudes than younger adults. Only when older men were compared with younger men in 24-h rhythm amplitude by simple t-test did any comparison involving amplitude achieve statistical significance (p < 0.05).

Monk, T. H.; Buysse, D. J.; Reynolds, C. F. 3rd; Kupfer, D. J.; Houck, P. R.

1995-01-01

85

Circadian rhythms in rheumatology - a glucocorticoid perspective  

PubMed Central

The hypothalamic-pituitary-adrenal (HPA) axis plays an important role in regulating and controlling immune responses. Dysfunction of the HPA axis has been implicated in the pathogenesis of rheumatoid arthritis (RA) and other rheumatic diseases. The impact of glucocorticoid (GC) therapy on HPA axis function also remains a matter of concern, particularly for longer treatment duration. Knowledge of circadian rhythms and the influence of GC in rheumatology is important: on the one hand we aim for optimal treatment of the daily undulating inflammatory symptoms, for example morning stiffness and swelling; on the other, we wish to disturb the HPA axis as little as possible. This review describes circadian rhythms in RA and other chronic inflammatory diseases, dysfunction of the HPA axis in RA and other rheumatic diseases and the recent concept of the hepato-hypothalamic-pituitary-adrenal-renal axis, the problem of adrenal suppression by GC therapy and how it can be avoided, and evidence that chronotherapy with modified release prednisone effective at 02:00 a.m. can inhibit proinflammatory sequelae of nocturnal inflammation better compared with GC administration in the morning but does not increase the risk of HPA axis insufficiency in RA. PMID:25608777

2014-01-01

86

A Plastic Clock: How Circadian Rhythms Respond to Environmental Cues in Drosophila  

Microsoft Academic Search

Circadian clocks synchronize the physiology and behavior of most animals with the day to night cycle. A fundamental property\\u000a of the molecular pacemakers generating circadian rhythms is their self-sustained nature: they keep oscillating even under\\u000a constant conditions, with a period close to, but not exactly, 24 h. However, circadian pacemakers have to be sensitive to\\u000a environmental cues to be beneficial. They

Raphaelle Dubruille; Patrick Emery

2008-01-01

87

Circadian Rhythms in Prokaryotes: Luciferase as a Reporter of Circadian Gene Expression in Cyanobacteria  

Microsoft Academic Search

We have used a luciferase reporter gene and continuous automated monitoring of bioluminescence to demonstrate unequivocally that cyanobacteria exhibit circadian behaviors that are fundamentally the same as circadian rhythms of eukaryotes. We also show that these rhythms can be studied by molecular methods in Synechococcus sp. PCC7942, a strain for which genetic transformation is well established. A promoterless segment of

Takao Kondo; Carl A. Strayer; Resham D. Kulkarni; Walter Taylor; Masahiro Ishiura; Susan S. Golden; Carl Hirschie Johnson

1993-01-01

88

Activity in the ferret: oestradiol effects and circadian rhythms  

NASA Technical Reports Server (NTRS)

The present study was conducted to determine whether oestradiol increases activity in the European ferret (Mustela furo), whether this effect is sexually dimorphic, and whether a 24-h rhythm is present in the ferret's daily activity. The activity of male and female adult, postpubertally gonadectomized ferrets was monitored while they were maintained singly on a 13:11 light-dark cycle, before and after implantation with oestradiol-17 beta. Gonadectomized male and female ferrets exhibited equal levels of activity, and neither sex exhibited a significant change in activity following oestradiol implantation. None of the ferrets exhibited a strong circadian rhythm, although weak 24-h rhythms and shorter harmonic rhythms were present. Golden hamsters (Mesocricetus auratus), monitored in an identical manner, exhibited strong circadian rhythms. It was concluded that oestradiol administration may not cause an increase in activity in the ferret, and that this species lacks a strong circadian activity rhythm.

Stockman, E. R.; Albers, H. E.; Baum, M. J.; Wurtman, R. J. (Principal Investigator)

1985-01-01

89

Synergistic interactions between the molecular and neuronal circadian networks drive robust behavioral circadian rhythms in Drosophila melanogaster.  

PubMed

Most organisms use 24-hr circadian clocks to keep temporal order and anticipate daily environmental changes. In Drosophila melanogaster CLOCK (CLK) and CYCLE (CYC) initiates the circadian system by promoting rhythmic transcription of hundreds of genes. However, it is still not clear whether high amplitude transcriptional oscillations are essential for circadian timekeeping. In order to address this issue, we generated flies in which the amplitude of CLK-driven transcription can be reduced partially (approx. 60%) or strongly (90%) without affecting the average levels of CLK-target genes. The impaired transcriptional oscillations lead to low amplitude protein oscillations that were not sufficient to drive outputs of peripheral oscillators. However, circadian rhythms in locomotor activity were resistant to partial reduction in transcriptional and protein oscillations. We found that the resilience of the brain oscillator is depending on the neuronal communication among circadian neurons in the brain. Indeed, the capacity of the brain oscillator to overcome low amplitude transcriptional oscillations depends on the action of the neuropeptide PDF and on the pdf-expressing cells having equal or higher amplitude of molecular rhythms than the rest of the circadian neuronal groups in the fly brain. Therefore, our work reveals the importance of high amplitude transcriptional oscillations for cell-autonomous circadian timekeeping. Moreover, we demonstrate that the circadian neuronal network is an essential buffering system that protects against changes in circadian transcription in the brain. PMID:24698952

Weiss, Ron; Bartok, Osnat; Mezan, Shaul; Malka, Yuval; Kadener, Sebastian

2014-04-01

90

Synergistic Interactions between the Molecular and Neuronal Circadian Networks Drive Robust Behavioral Circadian Rhythms in Drosophila melanogaster  

PubMed Central

Most organisms use 24-hr circadian clocks to keep temporal order and anticipate daily environmental changes. In Drosophila melanogaster CLOCK (CLK) and CYCLE (CYC) initiates the circadian system by promoting rhythmic transcription of hundreds of genes. However, it is still not clear whether high amplitude transcriptional oscillations are essential for circadian timekeeping. In order to address this issue, we generated flies in which the amplitude of CLK-driven transcription can be reduced partially (approx. 60%) or strongly (90%) without affecting the average levels of CLK-target genes. The impaired transcriptional oscillations lead to low amplitude protein oscillations that were not sufficient to drive outputs of peripheral oscillators. However, circadian rhythms in locomotor activity were resistant to partial reduction in transcriptional and protein oscillations. We found that the resilience of the brain oscillator is depending on the neuronal communication among circadian neurons in the brain. Indeed, the capacity of the brain oscillator to overcome low amplitude transcriptional oscillations depends on the action of the neuropeptide PDF and on the pdf-expressing cells having equal or higher amplitude of molecular rhythms than the rest of the circadian neuronal groups in the fly brain. Therefore, our work reveals the importance of high amplitude transcriptional oscillations for cell-autonomous circadian timekeeping. Moreover, we demonstrate that the circadian neuronal network is an essential buffering system that protects against changes in circadian transcription in the brain. PMID:24698952

Weiss, Ron; Bartok, Osnat; Mezan, Shaul; Malka, Yuval; Kadener, Sebastian

2014-01-01

91

Circadian rhythms and period expression in the Hawaiian cricket genus Laupala  

PubMed Central

Daily activity times and circadian rhythms of crickets have been a subject of behavioral and physiological study for decades. However, recent studies suggest that the underlying molecular mechanism of cricket endogenous clocks differ from the model of circadian rhythm generation in Drosophila. Here we examine the circadian free-running periods of walking and singing in two Hawaiian swordtail cricket species, Laupala cerasina and Laupala paranigra, that differ in the daily timing of mating related activities. Additionally, we examine variation in sequence and daily cycling of the period (per) gene transcript between these species. The species differed significantly in free-running period of singing, but did not differ significantly in the free-running period of locomotion. Like in Drosophila, per transcript abundance showed cycling consistent with a role in circadian rhythm generation. The amino acid differences identified between these species suggest a potential of the per gene in interspecific behavioral variation in Laupala. PMID:23436058

Fergus, Daniel J.; Shaw, Kerry L.

2013-01-01

92

Circadian rhythms and period expression in the Hawaiian cricket genus Laupala.  

PubMed

Daily activity times and circadian rhythms of crickets have been a subject of behavioral and physiological study for decades. However, recent studies suggest that the underlying molecular mechanism of cricket endogenous clocks differ from the model of circadian rhythm generation in Drosophila. Here we examine the circadian free-running periods of walking and singing in two Hawaiian swordtail cricket species, Laupala cerasina and Laupala paranigra, that differ in the daily timing of mating related activities. Additionally, we examine variation in sequence and daily cycling of the period (per) gene transcript between these species. The species differed significantly in free-running period of singing, but did not differ significantly in the free-running period of locomotion. Like in Drosophila, per transcript abundance showed cycling consistent with a role in circadian rhythm generation. The amino acid differences identified between these species suggest a potential of the per gene in interspecific behavioral variation in Laupala. PMID:23436058

Fergus, Daniel J; Shaw, Kerry L

2013-05-01

93

Manipulating circadian clock neuron firing rate resets molecular circadian rhythms and behavior.  

PubMed

To examine the interaction between molecular, electrical and behavioral circadian rhythms, we combined optogenetic manipulation of suprachiasmatic nucleus (SCN) firing rate with bioluminescence imaging and locomotor activity monitoring. Manipulating firing rate reset circadian rhythms both ex vivo and in vivo, and this resetting required spikes and network communication. This suggests that SCN firing rate is fundamental to circadian pacemaking as both an input to and output of the molecular clockworks. PMID:25643294

Jones, Jeff R; Tackenberg, Michael C; McMahon, Douglas G

2015-03-01

94

Preliminary characterization of persisting circadian rhythms during space flight  

NASA Technical Reports Server (NTRS)

In order to evaluate the function of the circadian timing system in space, the circadian rhythm of conidiation of the fungus Neurospora crassa was monitored in constant darkness on the STS 9 flight of the Space Shuttle Columbia. During the first 7 days of spaceflight many tubes showed a marked reduction in the apparent amplitude of the conidiation rhythm, and some cultures appeared arrhythmic. There was more variability in the growth rate and circadian rhythms of individual cultures in space than is usually seen on earth. The results of this experiment indicate that while the circadian rhythm of Neurospora conidiation can persist outside of the earth's environment, either the timekeeping process or its expression is altered in space.

Sultzman, F. M.

1984-01-01

95

Introduction: circadian rhythm and its disruption: impact on reproductive function.  

PubMed

Almost all forms of life have predictable daily or circadian rhythms in molecular, endocrine, and behavioral functions. In mammals, a central pacemaker located in the suprachiasmatic nuclei coordinates the timing of these rhythms. Daily light exposure that affects the retina of the eye directly influences this area, which is required to align endogenous processes to the appropriate time of day. The present "Views and Reviews" articles discuss the influence of circadian rhythms, especially nightly secretion of melatonin, on reproductive function and parturition. In addition, an examination is made of problems that arise from recurrent circadian rhythm disruption associated with changes in light exposure patterns common to modern day society. Finally, a possible solution to prevent disruptions in circadian phase markers by filtering out short wavelengths from nocturnal light is reviewed. PMID:24954773

Casper, Robert F; Gladanac, Bojana

2014-08-01

96

Recent advances in circadian rhythms in cardiovascular system  

PubMed Central

Growing evidence shows that intrinsic circadian clocks are tightly related to cardiovascular functions. The diurnal changes in blood pressure and heart rate are well known circadian rhythms. Endothelial function, platelet aggregation and thrombus formation exhibit circadian changes as well. The onset of many cardiovascular diseases (CVDs) or events, such as myocardial infarction, stroke, arrhythmia, and sudden cardiac death, also exhibits temporal trends. Furthermore, there is strong evidence from animal models and epidemiological studies showing that disruption of circadian rhythms is a significant risk factor for many CVDs, and the intervention of CVDs may have a time dependent effect. In this mini review, we summarized recent advances in our understanding of the relationship between circadian rhythm and cardiovascular physiology and diseases including blood pressure regulation and myocardial infarction.

Chen, Lihong; Yang, Guangrui

2015-01-01

97

Melatonin modulates the ERG circadian rhythm in crayfish.  

PubMed

One of the most important functions modulated by melatonin is the synchronization of circadian rhythms. In crayfish (Procambarus clarkii), we have obtained evidence that the amplitude of the electrical response to light of the retinal photoreceptors the receptor potential, is modified by the action of melatonin and that the magnitude of this action depends on the circadian time of melatonin application. In contrast, the electroretinogram (ERG) circadian rhythm can be synchronized by either single or periodic melatonin application. In this work we hypothesized that, in crayfish, melatonin acts on effectors and on pacemaker of ERG circadian rhythm as a non-photic synchronizer. Melatonin could be a hormone that sends a signal of darkness to the ERG circadian system. PMID:18313959

Solís-Chagoyán, Héctor; Mendoza-Vargas, Leonor; Fuentes-Pardo, Beatriz

2008-04-01

98

Dynamics of three coupled van der Pol oscillators with application to circadian rhythms  

E-print Network

Dynamics of three coupled van der Pol oscillators with application to circadian rhythms Kevin this system comes from the presence of circadian rhythms in the chemistry of the eyes. We model the circadian.elsevier.com/locate/cnsns #12;Our motivation for studying this system comes from the presence of circadian rhythms

Rand, Richard H.

99

p38 MAP kinase regulates circadian rhythms in Drosophila.  

PubMed

The large repertoire of circadian rhythms in diverse organisms depends on oscillating central clock genes, input pathways for entrainment, and output pathways for controlling rhythmic behaviors. Stress-activated p38 MAP Kinases (p38K), although sparsely investigated in this context, show circadian rhythmicity in mammalian brains and are considered part of the circadian output machinery in Neurospora. We find that Drosophila p38Kb is expressed in clock neurons, and mutants in p38Kb either are arrhythmic or have a longer free-running periodicity, especially as they age. Paradoxically, similar phenotypes are observed through either transgenic inhibition or activation of p38Kb in clock neurons, suggesting a requirement for optimal p38Kb function for normal free-running circadian rhythms. We also find that p38Kb genetically interacts with multiple downstream targets to regulate circadian locomotor rhythms. More specifically, p38Kb interacts with the period gene to regulate period length and the strength of rhythmicity. In addition, we show that p38Kb suppresses the arrhythmic behavior associated with inhibition of a second p38Kb target, the transcription factor Mef2. Finally, we find that manipulating p38K signaling in free-running conditions alters the expression of another downstream target, MNK/Lk6, which has been shown to cycle with the clock and to play a role in regulating circadian rhythms. These data suggest that p38Kb may affect circadian locomotor rhythms through the regulation of multiple downstream pathways. PMID:25403440

Vrailas-Mortimer, Alysia D; Ryan, Sarah M; Avey, Matthew J; Mortimer, Nathan T; Dowse, Harold; Sanyal, Subhabrata

2014-12-01

100

Circadian Rhythms of Neuroendocrine Dopaminergic Neuronal Activity in Ovariectomized Rats  

Microsoft Academic Search

Prolactin (PRL) secretion is inhibited by dopamine (DA) released from hypothalamic neuroendocrine neurons designated tuberoinfundibular (TIDA), tuberohypophyseal (THDA) and periventricular hypophyseal (PHDA) dopaminergic (DAergic) neurons. Since PRL is secreted in many physiological states with a circadian rhythm, the purpose of these experiments was to determine if patterns of neuroendocrine DAergic neuronal activity in rats are also circadian. The activity of

Michael T. Sellix; Marc E. Freeman

2003-01-01

101

Genetic basis of incidence and period length of circadian rhythm for locomotor activity in populations of a seed beetle.  

PubMed

Circadian rhythms are ubiquitous in a wide variety of organisms, although their genetic variation has been analyzed in only a few species. We found genetic differences in the circadian rhythm of adult locomotor activity among strains of the adzuki bean beetle, Callosobruchus chinensis, which differed in origin and have been maintained in isolation. All beetles in some strains clearly had free-running rhythms in constant darkness whereas most beetles in other strains were arrhythmic. The period of free-running rhythm varied from approximately 19 to 23 h between the strains. F(1) males from reciprocal crosses among strains with different periods of circadian rhythms had circadian periods that were intermediate between their parental strains. Segregation of the circadian rhythm appeared in the F(2) generation. These findings are consistent with the hypothesis that variation in the period length of circadian rhythm is explained by a major autosomal gene with additive effects and no dominance. This hypothesis was supported by the joint scaling test for the free-running period in the F(1) and F(2) generations. We discuss possible causes for genetic variation in circadian rhythm in the C. chinensis strains in terms of random factors and selection. PMID:20145671

Harano, T; Miyatake, T

2010-09-01

102

Pineal Function in Sparrows: Circadian Rhythms and Body Temperature  

Microsoft Academic Search

Deep body temperature of the house sparrow, Passer domesticus, was monitored continuously by radio telemetry. Pinealectomy abolished the normal circadian rhythm of body temperature in constant darkness, and significantly altered the amplitude of body temperature rhythms entrained to light cycles. The body temperature minima of pinealectomized birds never fell as low as those of unoperated birds regardless of the light

Sue Binkley; Edward Kluth; Michael Menaker

1971-01-01

103

Photic and Circadian Regulations of Melatonin Rhythms in Fishes  

Microsoft Academic Search

Photic and circadian regulations of melatonin rhythms in the pineal organ and the retina of several teleosts were studied to investigate the regulatory mechanisms of melatonin rhythms in fishes. In the eyecup preparations of the goldfish, Carassius auratus, both time of day and lighting conditions affected melatonin production, with high melatonin production observed only in the dark-treated group incubated during

Masayuki Iigo; Masayuki Hara; Ritsuko Ohtani-Kaneko; Kazuaki Hirata; Mitsuo Tabata; Katsumi Aida

1997-01-01

104

Original article Effects of light on human circadian rhythms  

E-print Network

system. The circadian rhythms (melatonin, cortisol, timing of sleep/wake) of individuals with different enucleated showed free run- ning melatonin and cortisol rhythms. Studies assessing the light-induced suppression of melatonin show the response to be intensity and wavelength dependent. In contrast to ocular

Paris-Sud XI, Université de

105

Pinealectomy abolishes the circadian rhythm of migratory restlessness  

Microsoft Academic Search

Pinealectomy of White-throated Sparrows (Zonotrichia albicollis) free-running under constant conditions in dim light abolishes the circadian rhythm of nocturnal spring and fall migratory restlessness (Zugunruhe) as well as the rhythm of summer “daytime” locomotor activity (Pigs. 1 and 2). Rhythmicity persists in sham-operated birds. Pinealectomized birds are synchronized by a light cycle but their activity rhythm decays to arrhythmicity when

J. P. McMillan

1972-01-01

106

Dopaminergic Regulation of Circadian Food Anticipatory Activity Rhythms in the Rat  

PubMed Central

Circadian activity rhythms are jointly controlled by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN) and by food-entrainable circadian oscillators (FEOs) located elsewhere. The SCN mediates synchrony to daily light-dark cycles, whereas FEOs generate activity rhythms synchronized with regular daily mealtimes. The location of FEOs generating food anticipation rhythms, and the pathways that entrain these FEOs, remain to be clarified. To gain insight into entrainment pathways, we developed a protocol for measuring phase shifts of anticipatory activity rhythms in response to pharmacological probes. We used this protocol to examine a role for dopamine signaling in the timing of circadian food anticipation. To generate a stable food anticipation rhythm, rats were fed 3h/day beginning 6-h after lights-on or in constant light for at least 3 weeks. Rats then received the D2 agonist quinpirole (1 mg/kg IP) alone or after pretreatment with the dopamine synthesis inhibitor ?-methylparatyrosine (AMPT). By comparison with vehicle injections, quinpirole administered 1-h before lights-off (19h before mealtime) induced a phase delay of activity onset prior to the next meal. Delay shifts were larger in rats pretreated with AMPT, and smaller following quinpirole administered 4-h after lights-on. A significant shift was not observed in response to the D1 agonist SKF81297. These results provide evidence that signaling at D2 receptors is involved in phase control of FEOs responsible for circadian food anticipatory rhythms in rats. PMID:24312417

Smit, Andrea N.; Patton, Danica F.; Michalik, Mateusz; Opiol, Hanna; Mistlberger, Ralph E.

2013-01-01

107

Pinealectomy does not affect the entrainment to light nor the generation of the circadian demand-feeding rhythms of rainbow trout.  

PubMed

The pineal organ and its secretory product melatonin are regarded as synchronizers of daily rhythms to the external light/dark (LD) cycle. In fish, the pineal organ acts as a direct photoreceptor, transducing light information into neural and humoral (melatonin) signals. In the present study, we investigate a possible role for the pineal organ and melatonin in the regulation of feeding rhythms of rainbow trout, Oncorhynchus mykiss. We used individual rainbow trout placed in an insulated room at constant temperature (14 degrees C). Fish were self-fed ad lib by means of self-feeders coupled to a computer that continuously recorded demand-feeding activity. Before and after pinealectomy, the fish were exposed to a LD cycle of 16:8 h and then constant light (LL) to test the effect of pinealectomy on demand-feeding rhythms. Feeding records revealed that trout fed exclusively during daytime (96% of feeding confined to the light phase), and that removal of the pineal organ did not disrupt this daily feeding profile, with synchronization to the LD cycle persisting. Moreover, the appearance of circadian feeding rhythms was not affected by pinealectomy: most of the operated fish free-ran with an average tau longer than 24 h. Plasma melatonin rhythms persisted in the pinealectomized trout, but with small amplitude. These results suggest that the pineal may not be the site of the pacemaker that controls feeding rhythms in trout, although further research is required to study the involvement of other photoperiod-transducing systems and melatonin (of nonpineal origin) in the regulation and expression of circadian rhythms in this species. PMID:10913784

Sánchez-Vázquez, F J; Iigo, M; Madrid, J A; Tabata, M

108

‘The clocks that time us’—circadian rhythms in neurodegenerative disorders  

PubMed Central

Circadian rhythms are physiological and behavioural cycles generated by an endogenous biological clock, the suprachiasmatic nucleus. The circadian system influences the majority of physiological processes, including sleep–wake homeostasis. Impaired sleep and alertness are common symptoms of neurodegenerative disorders, and circadian dysfunction might exacerbate the disease process. The pathophysiology of sleep–wake disturbances in these disorders remains largely unknown, and is presumably multifactorial. Circadian rhythm dysfunction is often observed in patients with Alzheimer disease, in whom it has a major impact on quality of life and represents one of the most important factors leading to institutionalization of patients. Similarly, sleep and circadian problems represent common nonmotor features of Parkinson disease and Huntington disease. Clinical studies and experiments in animal models of neurodegenerative disorders have revealed the progressive nature of circadian dysfunction throughout the course of neurodegeneration, and suggest strategies for the restoration of circadian rhythmicity involving behavioural and pharmacological interventions that target the sleep–wake cycle. In this Review, we discuss the role of the circadian system in the regulation of the sleep–wake cycle, and outline the implications of disrupted circadian timekeeping in neurodegenerative diseases. PMID:25385339

Videnovic, Aleksandar; Lazar, Alpar S.; Barker, Roger A.; Overeem, Sebastiaan

2015-01-01

109

Circadian rhythms in the short-tailed shrew, Blarina brevicauda.  

PubMed

Circadian rhythms of wheel running and feeding were measured in the short-tailed shrew. Shrews were strongly nocturnal, and their activity rhythms entrained to both long-day (LD 16:8) and short-day (LD 6:18) photocycles. Under conditions of continuous light (LL) or darkness (DD), the activity rhythms free-ran with average periodicities of 25.1 hours and 24.1 hours, respectively. In LL the level of activity was depressed, and in some cases wheel running was completely inhibited. No significant sex differences were observed in the period or amplitude of the monitored circadian rhythms. All shrews fed throughout the day and night; however, unlike in previous reports, ultradian periods of feeding behavior were not found. The results are related to Aschoff's four observations for the effect of light on activity rhythms in nocturnal rodents. PMID:2255728

Antipas, A J; Madison, D M; Ferraro, J S

1990-08-01

110

Circadian Rhythm Connections to Oxidative Stress: Implications for Human Health  

PubMed Central

Abstract Significance: Oxygen and circadian rhythmicity are essential in a myriad of physiological processes to maintain homeostasis, from blood pressure and sleep/wake cycles, down to cellular signaling pathways that play critical roles in health and disease. If the human body or cells experience significant stress, their ability to regulate internal systems, including redox levels and circadian rhythms, may become impaired. At cellular as well as organismal levels, impairment in redox regulation and circadian rhythms may lead to a number of adverse effects, including the manifestation of a variety of diseases such as heart diseases, neurodegenerative conditions, and cancer. Recent Advances: Researchers have come to an understanding as to the basics of the circadian rhythm mechanism, as well as the importance of the numerous species of oxidative stress components. The effects of oxidative stress and dysregulated circadian rhythms have been a subject of intense investigations since they were first discovered, and recent investigations into the molecular mechanisms linking the two have started to elucidate the bases of their connection. Critical Issues: While much is known about the mechanics and importance of oxidative stress systems and circadian rhythms, the front where they interact has had very little research focused on it. This review discusses the idea that these two systems are together intricately involved in the healthy body, as well as in disease. Future Directions: We believe that for a more efficacious management of diseases that have both circadian rhythm and oxidative stress components in their pathogenesis, targeting both systems in tandem would be far more successful. Antioxid. Redox Signal. 19, 192–208 PMID:23198849

Wilking, Melissa; Ndiaye, Mary; Mukhtar, Hasan

2013-01-01

111

Reversible phosphorylation subserves robust circadian rhythms by creating a switch in inactivating the positive element.  

PubMed

Reversible phosphorylation of proteins is ubiquitous in circadian systems, but the role it plays in generating rhythmicity is not completely understood. A common mechanism for most circadian rhythms involves a negative feedback loop between the positive and negative elements. Here, we built a minimal model for the Neurospora crassa circadian clock based on the core negative feedback loop and the protein FREQUENCY (FRQ)-dependent phosphorylation of the White Collar Complex (WCC). The model can reproduce basic features of the clock, such as the period length, phase relationship, and entrainment to light/dark cycles. We found that the activity of WCC can be controlled by FRQ in a switchlike manner owing to zero-order ultrasensitivity. WCC is inactivated when FRQ level crosses a threshold from below. As a result, low cooperativity in transcriptional activation is sufficient for circadian rhythms, and the level of active WCC exhibits spiky oscillations. Such oscillations are robust to molecular noise and may subserve controlling circadian output. Therefore, the core negative feedback together with phosphorylation of the positive element can ensure robust circadian rhythms. Our work provides insights into the critical roles of posttranslational modification in circadian clocks. PMID:19948115

Cheng, Zhang; Liu, Feng; Zhang, Xiao-Peng; Wang, Wei

2009-12-01

112

Robust Oscillations within the Interlocked Feedback Model of Drosophila Circadian Rhythm  

Microsoft Academic Search

A mechanism for generating circadian rhythms has been of major interest in recent years. After the discovery of per and tim, a model with a simple feedback loop involving per and tim has been proposed. However, it is recognized that the simple feedback model cannot account for phenotypes generated by various mutants. A recent report by Glossop, Lyons & Hardin

HIROKI R. UEDA; MASATOSHI HAGIWARA; HIROAKI KITANO

2001-01-01

113

An Antennal Circadian Clock and Circadian Rhythms in Peripheral Pheromone Reception in the Moth Spodoptera littoralis  

Microsoft Academic Search

Circadian rhythms are observed in mating behaviors in moths: females emit sex pheromones and males are attracted by these pheromones in rhythmic fashions. In the moth Spodoptera littoralis, we demonstrated the occurrence of a circadian oscillator in the antenna, the peripheral olfactory organ. We identified different clock genes, period (per), cryptochrome1 (cry1) and cryptochrome2 (cry2), in this organ. Using quantitative

Christine Merlin; Philippe Lucas; Didier Rochat; Marie-Christine François; Martine Maïbèche-Coisne; Emmanuelle Jacquin-Joly

2007-01-01

114

Circadian rhythms persist without transcription in a John S. O'Neill1,5  

E-print Network

Circadian rhythms persist without transcription in a eukaryote John S. O'Neill1,5 *, Gerben Van-line summary: Circadian rhythms in a eukaryote can be sustained soley by post- translational mechanisms which are conserved across taxa. #12;Circadian rhythms are ubiquitous in eukaryotes, and co-ordinate numerous aspects

Mesbah, Mounir

115

Employing Circadian Rhythms to Enhance Power and Reliability Saket Gupta, Broadcom Corporation  

E-print Network

A Employing Circadian Rhythms to Enhance Power and Reliability Saket Gupta, Broadcom Corporation (BTI), inspired by the notion of human circadian rhythms. The method works in two alternating phases. and Sapatnekar, S. S. 2012. Employing Circadian Rhythms to Enhance Power and Reliability. ACM Trans. Des. Autom

Sapatnekar, Sachin

116

Circadian rhythms in Neurospora crassa: Dynamics of the clock component frequency visualized using a fluorescent reporter  

E-print Network

Circadian rhythms in Neurospora crassa: Dynamics of the clock component frequency visualized using August 2009 Accepted 30 December 2009 Available online 4 January 2010 Keywords: Circadian rhythm m essential to the function of this organism's circadian rhythm. Increasingly, deciphering the coupling

Hasty, Jeff

117

Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest  

E-print Network

Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest Christopher E circadian rhythms constrain the rates of leaf and canopy gas exchange in an Amazonian forest over a day of the day. We attribute these cycles to circadian rhythms that are analogous to ones that have been reported

Goulden, Michael L.

118

An ASMT variant associated with bipolar disorder influences sleep and circadian rhythms: a pilot study  

E-print Network

references) 10 Keywords: sleep; actigraphy; melatonin; ASMT gene; bipolar disorder; circadian rhythms-associated functional variant involved in the melatonin synthesis pathway influences sleep and circadian rhythms1 An ASMT variant associated with bipolar disorder influences sleep and circadian rhythms: a pilot

Paris-Sud XI, Université de

119

The Impact of HIF1? on the Per2 Circadian Rhythm in Renal Cancer Cell Lines  

PubMed Central

In mammals, the circadian rhythm central generator consists of interactions among clock genes, including Per1/2/3, Cry1/2, Bmal1, and Clock. Circadian rhythm disruption may lead to increased risk of cancer in humans, and deregulation of clock genes has been implicated in many types of cancers. Among these genes, Per2 is reported to have tumor suppressor properties, but little is known about the correlation between Per2 and HIF, which is the main target of renal cell carcinoma (RCC) therapy. In this study, the rhythmic expression of the Per2 gene was not detectable in renal cancer cell lines, with the exception of Caki-2 cells. In Caki-2 cells, HIF1? increased the amplitude of Per2 oscillation by directly binding to the HIF-binding site located on the Per2 promoter. These results indicate that HIF1? may enhance the amplitude of the Per2 circadian rhythm. PMID:25333958

Okabe, Takashi; Kumagai, Megumi; Nakajima, Yoshihiro; Shirotake, Suguru; Kodaira, Kiichiro; Oyama, Masafumi; Ueno, Munehisa; Ikeda, Masaaki

2014-01-01

120

Loss of dopamine disrupts circadian rhythms in a mouse model of Parkinson's disease.  

PubMed

Although a wide range of physiological functions regulated by dopamine (DA) display circadian variations, the role of DA in the generation and/or modulation of these rhythms is unknown. In Parkinson's disease (PD) patients, in addition to the classical motor symptoms, disturbances of the pattern of daily rest/wake cycles are common non-motor symptoms. We investigated daily and circadian rhythms of rest/activity behaviors in a transgenic MitoPark mouse model with selective inactivation of mitochondrial transcription factor A (Tfam) resulting in a slow and progressive degeneration of DA neurons in midbrain structures. Correlated with this, MitoPark mice show a gradual reduction in locomotor activity beginning at about 20weeks of age. In a light-dark cycle, MitoPark mice exhibit a daily pattern of rest/activity rhythms that shows an age-dependent decline in both the amplitude and the stability of the rhythm, coupled with an increased fragmentation of day/night activities. When the circadian system is challenged by exposure to constant darkness or constant light conditions, control littermates retain a robust free-running circadian locomotor rhythm, whereas in MitoPark mice, locomotor rhythms are severely disturbed or completely abolished. Re-exposure to a light/dark cycle completely restores daily locomotor rhythms. MitoPark mice and control littermates express similar masking behaviors under a 1h light/1h dark regime, suggesting that the maintenance of a daily pattern of rest/activity in arrhythmic MitoPark mice can be attributed to the acute inhibitory and stimulatory effects of light and darkness. These results imply that, in addition to the classical motor abnormalities observed in PD, the loss of the midbrain DA neurons leads to impairments of the circadian control of rest/activity rhythms. PMID:25171792

Fifel, Karim; Cooper, Howard M

2014-11-01

121

Light as a central modulator of circadian rhythms, sleep and affect.  

PubMed

Light has profoundly influenced the evolution of life on earth. As widely appreciated, light enables us to generate images of our environment. However, light - through intrinsically photosensitive retinal ganglion cells (ipRGCs) - also influences behaviours that are essential for our health and quality of life but are independent of image formation. These include the synchronization of the circadian clock to the solar day, tracking of seasonal changes and the regulation of sleep. Irregular light environments lead to problems in circadian rhythms and sleep, which eventually cause mood and learning deficits. Recently, it was found that irregular light can also directly affect mood and learning without producing major disruptions in circadian rhythms and sleep. In this Review, we discuss the indirect and direct influence of light on mood and learning, and provide a model for how light, the circadian clock and sleep interact to influence mood and cognitive functions. PMID:24917305

LeGates, Tara A; Fernandez, Diego C; Hattar, Samer

2014-07-01

122

Circadian rhythms in electric waveform structure and rate in the electric fish Brachyhypopomus pinnicaudatus  

E-print Network

Circadian rhythms in electric waveform structure and rate in the electric fish Brachyhypopomus regulation of circadian rhythm expression. Previous studies asserting that these oscillations are circadian in strength and magnitude of the circadian oscillations; male oscillations were stronger and larger. All three

Stoddard, Philip

123

JOURNAL OF BIOLOGICAL RHYTHMS / June 1999Olde Scheper et al. / MOLECULAR CIRCADIAN CLOCKS A Model of Molecular Circadian Clocks  

E-print Network

JOURNAL OF BIOLOGICAL RHYTHMS / June 1999Olde Scheper et al. / MOLECULAR CIRCADIAN CLOCKS A Model of Molecular Circadian Clocks: Multiple Mechanisms for Phase Shifting and a Requirement for Strong Nonlinear, the Netherlands Abstract A fundamental question in the field of circadian rhythms concerns the biochemical

van Pelt, Jaap

124

Sleep, circadian rhythms, and the pathogenesis of Alzheimer Disease  

PubMed Central

Disturbances in the sleep–wake cycle and circadian rhythms are common symptoms of Alzheimer Disease (AD), and they have generally been considered as late consequences of the neurodegenerative processes. Recent evidence demonstrates that sleep–wake and circadian disruption often occur early in the course of the disease and may even precede the development of cognitive symptoms. Furthermore, the sleep–wake cycle appears to regulate levels of the pathogenic amyloid-beta peptide in the brain, and manipulating sleep can influence AD-related pathology in mouse models via multiple mechanisms. Finally, the circadian clock system, which controls the sleep–wake cycle and other diurnal oscillations in mice and humans, may also have a role in the neurodegenerative process. In this review, we examine the current literature related to the mechanisms by which sleep and circadian rhythms might impact AD pathogenesis, and we discuss potential therapeutic strategies targeting these systems for the prevention of AD.

Musiek, Erik S; Xiong, David D; Holtzman, David M

2015-01-01

125

Minimum Criteria for DNA Damage-Induced Phase Advances in Circadian Rhythms  

PubMed Central

Robust oscillatory behaviors are common features of circadian and cell cycle rhythms. These cyclic processes, however, behave distinctively in terms of their periods and phases in response to external influences such as light, temperature, nutrients, etc. Nevertheless, several links have been found between these two oscillators. Cell division cycles gated by the circadian clock have been observed since the late 1950s. On the other hand, ionizing radiation (IR) treatments cause cells to undergo a DNA damage response, which leads to phase shifts (mostly advances) in circadian rhythms. Circadian gating of the cell cycle can be attributed to the cell cycle inhibitor kinase Wee1 (which is regulated by the heterodimeric circadian clock transcription factor, BMAL1/CLK), and possibly in conjunction with other cell cycle components that are known to be regulated by the circadian clock (i.e., c-Myc and cyclin D1). It has also been shown that DNA damage-induced activation of the cell cycle regulator, Chk2, leads to phosphorylation and destruction of a circadian clock component (i.e., PER1 in Mus or FRQ in Neurospora crassa). However, the molecular mechanism underlying how DNA damage causes predominantly phase advances in the circadian clock remains unknown. In order to address this question, we employ mathematical modeling to simulate different phase response curves (PRCs) from either dexamethasone (Dex) or IR treatment experiments. Dex is known to synchronize circadian rhythms in cell culture and may generate both phase advances and delays. We observe unique phase responses with minimum delays of the circadian clock upon DNA damage when two criteria are met: (1) existence of an autocatalytic positive feedback mechanism in addition to the time-delayed negative feedback loop in the clock system and (2) Chk2-dependent phosphorylation and degradation of PERs that are not bound to BMAL1/CLK. PMID:19424508

Csikász-Nagy, Attila

2009-01-01

126

Circadian rhythms of temperature and activity in obese and lean Zucker rats  

NASA Technical Reports Server (NTRS)

The circadian timing system is important in the regulation of feeding and metabolism, both of which are aberrant in the obese Zucker rat. This study tested the hypothesis that these abnormalities involve a deficit in circadian regulation by examining the circadian rhythms of body temperature and activity in lean and obese Zucker rats exposed to normal light-dark cycles, constant light, and constant dark. Significant deficits in both daily mean and circadian amplitude of temperature and activity were found in obese Zucker female rats relative to lean controls in all lighting conditions. However, the circadian period of obese Zucker rats did not exhibit differences relative to lean controls in either of the constant lighting conditions. These results indicate that although the circadian regulation of temperature and activity in obese Zucker female rats is in fact depressed, obese rats do exhibit normal entrainment and pacemaker functions in the circadian timing system. The results suggest a deficit in the process that generates the amplitude of the circadian rhythm.

Murakami, D. M.; Horwitz, B. A.; Fuller, C. A.

1995-01-01

127

Circadian rhythm of cortisol and estradiol in healthy women  

Microsoft Academic Search

\\u000aCIRCADIAN RHYTHM OF CORTISOL AND ESTRADIOL IN HEALTHY WOMEN\\u000aby\\u000aKARYN G. BUTLER\\u000aAUGUST 2011\\u000aAdvisor: Dr. Jean E. Davis\\u000aMajor: Nursing\\u000aDegree: Doctor of Philosophy\\u000aDaily variation in human processes and behaviors has been identified for centuries. Study of these circadian rhythms demonstrates their role in human health. Sickness behaviors include alterations in affect, sleep quality and energy. The

Karyn G. Butler

2011-01-01

128

Observer design for a core circadian rhythm network.  

PubMed

The paper investigates the observer design for a core circadian rhythm network in Drosophila and Neurospora. Based on the constructed highly nonlinear differential equation model and the recently proposed graphical approach, we design a rather simple observer for the circadian rhythm oscillator, which can well track the state of the original system for various input signals. Numerical simulations show the effectiveness of the designed observer. Potential applications of the related investigations include the real-world control and experimental design of the related biological networks. PMID:25121122

Zhang, Yuhuan

2014-01-01

129

Multiparameter data acquisition systems for studies of circadian rhythms  

SciTech Connect

Long-term, simultaneous monitoring of multiple metabolic circadian cycles such as energy metabolism, animal activity, and body temperature together have revealed ultradian fine-structure rhythms which are dependent on circadian phase and the perturbations of environmental influences. Because of the variation between individual animals, these experiments need to have large sample sizes for each experimental condition. To this end we have designed, constructed and used four microcomputer controlled data acquisition systems to collect circadian data from individually housed rats and mice. 11 refs., 6 figs.

Groh, K.R.; Ehret, C.F.; Eisler, W.J. Jr.; LeBuis, D.A.

1985-01-01

130

Circadian rhythms in anesthesia and critical care medicine: potential importance of circadian disruptions.  

PubMed

The rotation of the earth and associated alternating cycles of light and dark--the basis of our circadian rhythms--are fundamental to human biology and culture. However, it was not until 1971 that researchers first began to describe the molecular mechanisms for the circadian system. During the past few years, groundbreaking research has revealed a multitude of circadian genes affecting a variety of clinical diseases, including diabetes, obesity, sepsis, cardiac ischemia, and sudden cardiac death. Anesthesiologists, in the operating room and intensive care units, manage these diseases on a daily basis as they significantly affect patient outcomes. Intriguingly, sedatives, anesthetics, and the intensive care unit environment have all been shown to disrupt the circadian system in patients. In the current review, we will discuss how newly acquired knowledge of circadian rhythms could lead to changes in clinical practice and new therapeutic concepts. PMID:25294583

Brainard, Jason; Gobel, Merit; Bartels, Karsten; Scott, Benjamin; Koeppen, Michael; Eckle, Tobias

2015-03-01

131

PPAR{alpha} is a potential therapeutic target of drugs to treat circadian rhythm sleep disorders  

SciTech Connect

Recent progress at the molecular level has revealed that nuclear receptors play an important role in the generation of mammalian circadian rhythms. To examine whether peroxisome proliferator-activated receptor alpha (PPAR{alpha}) is involved in the regulation of circadian behavioral rhythms in mammals, we evaluated the locomotor activity of mice administered with the hypolipidemic PPAR{alpha} ligand, bezafibrate. Circadian locomotor activity was phase-advanced about 3 h in mice given bezafibrate under light-dark (LD) conditions. Transfer from LD to constant darkness did not change the onset of activity in these mice, suggesting that bezafibrate advanced the phase of the endogenous clock. Surprisingly, bezafibrate also advanced the phase in mice with lesions of the suprachiasmatic nucleus (SCN; the central clock in mammals). The circadian expression of clock genes such as period2, BMAL1, and Rev-erb{alpha} was also phase-advanced in various tissues (cortex, liver, and fat) without affecting the SCN. Bezafibrate also phase-advanced the activity phase that is delayed in model mice with delayed sleep phase syndrome (DSPS) due to a Clock gene mutation. Our results indicated that PPAR{alpha} is involved in circadian clock control independently of the SCN and that PPAR{alpha} could be a potent target of drugs to treat circadian rhythm sleep disorders including DSPS.

Shirai, Hidenori [Clock Cell Biology Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8566 (Japan); Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8502 (Japan); Oishi, Katsutaka [Clock Cell Biology Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8566 (Japan); Kudo, Takashi [Division of Physiology and Pharmacology, School of Science and Engineering, Waseda University, Nishitokyo, Tokyo 202-0021 (Japan); Shibata, Shigenobu [Division of Physiology and Pharmacology, School of Science and Engineering, Waseda University, Nishitokyo, Tokyo 202-0021 (Japan); Ishida, Norio [Clock Cell Biology Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8566 (Japan) and Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8502 (Japan)]. E-mail: n.ishida@aist.go.jp

2007-06-08

132

Cryptochrome restores dampened circadian rhythms and promotes healthspan in aging Drosophila  

PubMed Central

Summary Circadian clocks generate daily rhythms in molecular, cellular, and physiological functions providing temporal dimension to organismal homeostasis. Recent evidence suggests two-way relationship between circadian clocks and aging. While disruption of the circadian clock leads to premature aging in animals, there is also age-related dampening of output rhythms such as sleep/wake cycles and hormonal fluctuations. Decay in the oscillations of several clock genes was recently reported in aged fruit flies, but mechanisms underlying these age-related changes are not understood. We report that the circadian light-sensitive protein CRYPTOCHROME (CRY), is significantly reduced at both mRNA and protein levels in heads of old Drosophila melanogaster. Restoration of CRY using the binary GAL4/UAS system in old flies significantly enhanced the mRNA oscillatory amplitude of several genes involved in the clock mechanism. Flies with CRY overexpressed in all clock cells maintained strong rest/activity rhythms in constant darkness late in life when rhythms were disrupted in most control flies. WE also observed a remarkable extension of healthspan in flies with elevated CRY. Conversely, CRY deficient mutants showed accelerated functional decline and accumulated greater oxidative damage. Interestingly, overexpression of CRY in central clock neurons alone was not sufficient to restore rest/activity rhythms or extend healthspan. Together, these data suggest novel anti-aging functions of CRY and indicate that peripheral clocks play an active role in delaying behavioral and physiological aging. PMID:23692507

Rakshit, Kuntol; Giebultowicz, Jadwiga M.

2013-01-01

133

Circadian rhythms in human performance and mood under constant conditions  

NASA Technical Reports Server (NTRS)

This study explored the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, subjective alertness and well-being. Seventeen healthy young adults were studied under 36 h of 'unmasking' conditions (constant wakeful bedrest, temporal isolation, homogenized 'meals') during which rectal temperatures were measured every minute, and plasma cortisol and plasma melatonin measured every 20 min. Hourly subjective ratings of global vigour (alertness) and affect (well-being) were obtained followed by one of two performance batteries. On odd-numbered hours performance (speed and accuracy) of serial search, verbal reasoning and manual dexterity tasks was assessed. On even-numbered hours, performance (% hits, response speed) was measured at a 25-30 min visual vigilance task. Performance of all tasks (except search accuracy) showed a significant time of day variation usually with a nocturnal trough close to the trough in rectal temperature. Performance rhythms appeared not to reliably differ with working memory load. Within subjects, predominantly positive correlations emerged between good performance and higher temperatures and better subjective alertness; predominantly negative correlations between good performance and higher plasma levels of cortisol and melatonin. Temperature and cortisol rhythms correlated with slightly more performance measures (5/7) than did melatonin rhythms (4/7). Global vigour correlated about as well with performance (5/7) as did temperature, and considerably better than global affect (1/7). In conclusion: (1) between-task heterogeneity in circadian performance rhythms appeared to be absent when the sleep/wake cycle was suspended; (2) temperature (positively), cortisol and melatonin (negatively) appeared equally good as circadian correlates of performance, and (3) subjective alertness correlated with performance rhythms as well as (but not better than) body temperature, suggesting that performance rhythms were not directly mediated by rhythms in subjective alertness.

Monk, T. H.; Buysse, D. J.; Reynolds, C. F. 3rd; Berga, S. L.; Jarrett, D. B.; Begley, A. E.; Kupfer, D. J.

1997-01-01

134

Circadian Rhythms: In the Loop at Last  

NSDL National Science Digital Library

This Viewpoint compares and contrasts the circadian clocks of mammals and of Drosophila, emphasizing how different players are used to create the same basic script. Both the general script and the specific details of the murine and Drosophila circadian pathways are available at Science's Signal Transduction Knowledge Environment Connections Maps.

Russell N. Van Gelder (Washington University; Department of Ophthalmology and Visual Sciences/Department of Molecular Biology and Pharmacology)

2003-06-06

135

ANIMAL RESPONSES TO CIRCADIAN RHYTHMS IN FORAGE QUALITY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Net photosynthesis and respiration in growing plants cause a circadian rhythm in forage quality. Soluble sugar concentrations increase in plants during the day causing a dilution in ADF and NDF. Herbivores show a strong preference for afternoon (PM) vs morning (AM) harvested forage. Cattle, sheep, g...

136

Cell signaling, receptors, electrical effects and therapy in circadian rhythm.  

PubMed

Circadian rhythm has been the object of much attention. This review addresses the aspects of cell signaling, receptors, therapy and electrical effects in a multifaceted fashion. The pineal gland, which produces the important hormones melatonin and serotonin, exerts a prominent influence, in addition to the supraschiasmatic nucleus. Many aspects involve free radicals which have played a widespread role in biochemistry. PMID:23914781

Kovacic, Peter; Somanathan, Ratnasamy

2013-10-01

137

Development of Heart Rate Circadian Rhythm in Chickens *, R. Akiyamab  

E-print Network

Development of Heart Rate Circadian Rhythm in Chickens K. Moriyaa *, R. Akiyamab , E.M. Dzialowskic, University of North Texas, Denton, Texas, USA ABSTRACT In chick embryos, various instantaneous heart rate of mean heart rate (MHR) have been elucidated. IHR changes have also measured in newly hatched and young

Burggren, Warren

138

CIRCADIAN RHYTHMS: Integrating Circadian Timekeeping with Cellular Physiology  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required: Models of circadian timekeeping mechanisms in plants, flies, and mammals are expanding to include intracellular small-molecule signals.

Marie C. Harrisingh (Yale School of Medicine; Department of Cellular and Molecular Physiology)

2008-05-16

139

Microarray analysis of natural socially regulated plasticity in circadian rhythms of honey bees.  

PubMed

Honey bee workers care for ("nurse") the brood around the clock without circadian rhythmicity, but then they forage outside with strong circadian rhythms and a consolidated nightly rest. This chronobiological plasticity is associated with variation in the expression of the canonical "clock genes" that regulate the circadian clock: nurse bees show no brain rhythms of expression, while foragers do. These results suggest that the circadian system is organized differently in nurses and foragers. Nurses switch to activity with circadian rhythms shortly after being removed from the hive, suggesting that at least some clock cells in their brain continue to measure time while in the hive. We performed a microarray genome-wide survey to determine general patterns of brain gene expression in nurses and foragers sampled around the clock. We found 160 and 541 transcripts that exhibited significant sinusoidal oscillations in nurses and foragers, respectively, with peaks of expression distributed throughout the day in both task groups. Consistent with earlier studies, transcripts of genes involved in circadian rhythms, including Clockwork Orange that has not been studied before in bees, oscillated in foragers but not in nurses. The oscillating transcripts also were enriched for genes involved in the visual system, "development" and "response to stimuli" (foragers), "muscle contraction" and "microfilament motor gene expression" (nurses), and "generation of precursor metabolites" and "energy" (both). Transcripts of genes encoding P450 enzymes oscillated in both nurses and foragers but with a different phase. This study identified new putative clock-controlled genes in the honey bee and suggests that some brain functions show circadian rhythmicity even in nurse bees that are active around the clock. PMID:22306970

Rodriguez-Zas, Sandra L; Southey, Bruce R; Shemesh, Yair; Rubin, Elad B; Cohen, Mira; Robinson, Gene E; Bloch, Guy

2012-02-01

140

Microarray Analysis of Natural Socially-Regulated Plasticity in Circadian Rhythms of Honey Bees  

PubMed Central

Honey bee workers care for ("nurse") the brood around the clock without circadian rhythmicity, but then they forage outside with strong circadian rhythms and a consolidated nightly rest. This chronobiological plasticity is associated with variation in the expression of the canonical “clock genes” that regulate the circadian clock: nurse bees show no brain rhythms of expression, while foragers do. These results suggest that the circadian system is organized differently in nurses and foragers. Nurses switch to activity with circadian rhythms shortly after removed from the hive suggesting that at least some clock cells in their brain continue to measure time while in the hive. We performed a microarray genome-wide survey to determine general patterns of brain gene expression in nurses and foragers sampled around the clock. We found 160 and 541 transcripts that exhibited significant sinusoidal oscillations in nurses and foragers, respectively, with peaks of expression distributed throughout the day in both task groups. Consistent with earlier studies, transcripts of genes involved in circadian rhythms, including Clockwork Orange that has not been studied before in bees, oscillated in foragers but not in nurses. The oscillating transcripts also were enriched for genes involved in the visual system, “development” and “response to stimuli” (foragers), “muscle contraction” and “microfilament motor gene expression” (nurses), and “generation of precursor metabolites” and “energy” (both). Transcripts of genes encoding P450 enzymes oscillated in both nurses and foragers but with a different phase. This study identified new putative clock-controlled genes in the honey bee and suggests that some brain functions show circadian rhythmicity even in nurse bees that are active around the clock. PMID:22306970

Rodriguez-Zas, Sandra L.; Southey, Bruce R.; Shemesh, Yair; Rubin, Elad B.; Cohen, Mira; Robinson, Gene E.; Bloch, Guy

2012-01-01

141

CIRCADIAN RHYTHMS Marking Time for a Kingdom  

NSDL National Science Digital Library

The author provides perspective on a study reported on page 483 of this issue. Findings from this study identifying a crucial circadian gene in hamsters represents "a major breakthrough for time-conscious mammals".

Michael Young (The Rockefeller University; Laboratory of Genetics and National Science Foundation Center for Biological Timing)

2000-04-21

142

CIRCADIAN RHYTHMS: Daily Watch on Metabolism  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required: Plants and animals adjust responses to their environments through small molecules, including metabolites, which interact with their circadian clocks.

Takato Imaizumi (University of California, San Diego; Section of Cell and Developmental Biology)

2007-12-14

143

Light and Gravity Effects on Circadian Rhythms of Rhesus Macaques  

NASA Technical Reports Server (NTRS)

Temporal integration of a biological organism's physiological, behavioral and biochemical systems depends upon its circadian timing system. The endogenous period of this timing system is typically synchronized to the 24- hour day by environmental cues. The daily alternation of light and dark has long been known as one of the most potent environmental synchronizers influencing the circadian timing system. Alterations in the lighting environment (length or intensity of light exposure) can also affect the homeostatic state of the organism. A series of experiments was performed using rhesus monkeys with the objective of defining the fundamental properties of the circadian rhythm of body temperature. Three major experiments were performed in addition to several preliminary studies. These experiments explored 1.) the response of the rhesus body temperature rhythm to varying day length and light intensity; 2.) the response of the body temperature rhythm to light exposure as a function of time of day; and 3.) the characteristics of the metabolic heat production rhythm which is responsible for the daily cycle in body temperature. Results of these three completed experiments will be reported here. In addition, preliminary experiments were also performed in social entrainment of rhesus circadian rhythms and the properties of rhesus body temperature rhythms in constant conditions, where no external time cues were provided. Four adult male rhesus monkeys served as subjects in all experiments. All experiments were performed at the California Regional Primate Research Center. Each animal was implanted with a biotelemetry unit that measured deep body temperature. All surgeries were performed by a board certified veterinary surgeon under sterile conditions. The biotelemetry implants also provided an index of activity level in each animal. For metabolic heat production measurements, oxygen consumption and carbon dioxide production were measured and the caloric equivalent of these was calculated. Specific methodologies are described in detail.

Fuller, Charles

1997-01-01

144

Neuroimaging, cognition, light and circadian rhythms  

PubMed Central

In humans, sleep and wakefulness and the associated cognitive processes are regulated through interactions between sleep homeostasis and the circadian system. Chronic disruption of sleep and circadian rhythmicity is common in our society and there is a need for a better understanding of the brain mechanisms regulating sleep, wakefulness and associated cognitive processes. This review summarizes recent investigations which provide first neural correlates of the combined influence of sleep homeostasis and circadian rhythmicity on cognitive brain activity. Markers of interindividual variations in sleep-wake regulation, such as chronotype and polymorphisms in sleep and clock genes, are associated with changes in cognitive brain responses in subcortical and cortical areas in response to manipulations of the sleep-wake cycle. This review also includes recent data showing that cognitive brain activity is regulated by light, which is a powerful modulator of cognition and alertness and also directly impacts sleep and circadian rhythmicity. The effect of light varied with age, psychiatric status, PERIOD3 genotype and changes in sleep homeostasis and circadian phase. These data provide new insights into the contribution of demographic characteristics, the sleep-wake cycle, circadian rhythmicity and light to brain functioning. PMID:25071478

Gaggioni, Giulia; Maquet, Pierre; Schmidt, Christina; Dijk, Derk-Jan; Vandewalle, Gilles

2014-01-01

145

Sleep and circadian rhythm disruption in schizophrenia†  

PubMed Central

Background Sleep disturbances comparable with insomnia occur in up to 80% of people with schizophrenia, but very little is known about the contribution of circadian coordination to these prevalent disruptions. Aims A systematic exploration of circadian time patterns in individuals with schizophrenia with recurrent sleep disruption. Method We examined the relationship between sleep-wake activity, recorded actigraphically over 6 weeks, along with ambient light exposure and simultaneous circadian clock timing, by collecting weekly 48 h profiles of a urinary metabolite of melatonin in 20 out-patients with schizophrenia and 21 healthy control individuals matched for age, gender and being unemployed. Results Significant sleep/circadian disruption occurred in all the participants with schizophrenia. Half these individuals showed severe circadian misalignment ranging from phase-advance/delay to non-24 h periods in sleep-wake and melatonin cycles, and the other half showed patterns from excessive sleep to highly irregular and fragmented sleep epochs but with normally timed melatonin production. Conclusions Severe circadian sleep/wake disruptions exist despite stability in mood, mental state and newer antipsychotic treatment. They cannot be explained by the individuals' level of everyday function. PMID:22194182

Wulff, Katharina; Dijk, Derk-Jan; Middleton, Benita; Foster, Russell G.; Joyce, Eileen M.

2012-01-01

146

Circadian Rhythms Confer a Higher Level of Fitness to Arabidopsis Plants1  

E-print Network

Circadian Rhythms Confer a Higher Level of Fitness to Arabidopsis Plants1 Rachel M. Green, Sonia, P.O. Box 160606, University of California, Los Angeles, California 90095­1606 Circadian rhythms have expression of the CCA1 (CIRCADIAN CLOCK ASSOCIATED 1) gene in Arabidopsis plants (CCA1-ox) results in loss

Tobin, Elaine

147

Food-entrained circadian rhythms are sustained in arrhythmic Clk/Clk mutant mice  

E-print Network

Food-entrained circadian rhythms are sustained in arrhythmic Clk/Clk mutant mice SiNae Pitts,1 in final form 19 March 2003 Pitts, SiNae, Elizabeth Perone, and Rae Silver. Food- entrained circadian of the suprachiasmatic nucleus (SCN). Circadian rhythms within the SCN depend on transcription- translation feedback

Silver, Rae

148

Endogenous circadian rhythm in an index of cardiac vulnerability independent of changes in behavior  

E-print Network

Endogenous circadian rhythm in an index of cardiac vulnerability independent of changes in behavior, influences from the endogenous circadian pacemaker independent from behaviors may also affect cardiac control features of the healthy human heartbeat have an endogenous circadian rhythm that brings the features closer

Stanley, H. Eugene

149

Circadian rhythms on hypothalamicpituitaryadrenal axis hormones and cytokines of collagen induced arthritis in rats  

E-print Network

Circadian rhythms on hypothalamic­pituitary­adrenal axis hormones and cytokines of collagen induced whether circadian rhythms of the hormones of the hypothalamic­pituitary­adrenal (HPA) axis are associated with corresponding circadian fluctuations in cytokines in a rat model of collagen-induced arthritis (CIA). CIA

Li, Shao

150

Cellular/Molecular Cellular Location and Circadian Rhythm of Expression of the  

E-print Network

for melatonin synthesis, aryl alkylamine N-acetyltransferase (AA-NAT), was governed by a circadian rhythm rhythm of melatonin produc- tion (Cahill and Besharse, 1993). More recent studies on Xenopus retina have, see Ander- son and Green, 2000). The mammalian retina also exhibits circadian rhythms of melatonin

Silver, Rae

151

Sleep and Circadian Rhythms in Four Orbiting Astronauts  

NASA Technical Reports Server (NTRS)

INTRODUCTION The study of human sleep and circadian rhythms in space has both operational and scientific significance. Operationally, U.S. Spaceflight is moving away from brief missions with durations of less than one week. Most space shuttle missions now last two weeks or more, and future plans involving space stations, lunar bases and interplanetary missions all presume that people will be living away from the gravity and time cues of earth for months at a time. Thus, missions are moving away from situations where astronauts can "tough it out" for comparatively brief durations, to situations where sleep and circadian disruptions are likely to become chronic, and thus resistant to short term pharmacological or behavioral manipulations. As well as the operational significance, there is a strong theoretical imperative for studying the sleep and circadian rhythms of people who are removed from the gravity and time cues of earth. Like other animals, in humans, the Circadian Timekeeping System (CTS) is entrained to the correct period (24h) and temporal orientation by various time cues ("zeitgebers"), the most powerful of which is the alternation of daylight and darkness. In leaving Earth, astronauts are removing themselves from the prime zeitgeber of their circadian system -- the 24h alternation of daylight and darkness.

Monk, Timothy H.; Buysse, Daniel J.; Billy, Bart D.; Kennedy, Kathy S.; Willrich, Linda M.

1999-01-01

152

Calculating activation energies for temperature compensation in circadian rhythms  

NASA Astrophysics Data System (ADS)

Many biological species possess a circadian clock, which helps them anticipate daily variations in the environment. In the absence of external stimuli, the rhythm persists autonomously with a period of approximately 24 h. However, single pulses of light, nutrients, chemicals or temperature can shift the clock phase. In the case of light- and temperature-cycles, this allows entrainment of the clock to cycles of exactly 24 h. Circadian clocks have the remarkable property of temperature compensation, that is, the period of the circadian rhythm remains relatively constant within a physiological range of temperatures. For several organisms, temperature-regulated processes within the circadian clock have been identified in recent years. However, how these processes contribute to temperature compensation is not fully understood. Here, we theoretically investigate temperature compensation in general oscillatory systems. It is known that every oscillator can be locally temperature compensated around a reference temperature, if reactions are appropriately balanced. A balancing is always possible if the control coefficient with respect to the oscillation period of at least one reaction in the oscillator network is positive. However, for global temperature compensation, the whole physiological temperature range is relevant. Here, we use an approach which leads to an optimization problem subject to the local balancing principle. We use this approach to analyse different circadian clock models proposed in the literature and calculate activation energies that lead to temperature compensation.

Bodenstein, C.; Heiland, I.; Schuster, S.

2011-10-01

153

Age, circadian rhythms, and sleep loss in flight crews  

NASA Technical Reports Server (NTRS)

Age-related changes in trip-induced sleep loss, personality, and the preduty temperature rhythm were analyzed in crews from various flight operations. Eveningness decreased with age. The minimum of the baseline temperature rhythm occurred earlier with age. The amplitude of the baseline temperature rhythm declined with age. Average daily percentage sleep loss during trips increased with age. Among crewmembers flying longhaul flight operations, subjects aged 50-60 averaged 3.5 times more sleep loss per day than subjects aged 20-30. These studies support previous findings that evening types and subjects with later peaking temperature rhythms adapt better to shift work and time zone changes. Age and circadian type may be important considerations for duty schedules and fatigue countermeasures.

Gander, Philippa H.; Nguyen, DE; Rosekind, Mark R.; Connell, Linda J.

1993-01-01

154

Design and analysis of temperature preference behavior and its circadian rhythm in Drosophila.  

PubMed

The circadian clock regulates many aspects of life, including sleep, locomotor activity, and body temperature (BTR) rhythms(1) (,) (2). We recently identified a novel Drosophila circadian output, called the temperature preference rhythm (TPR), in which the preferred temperature in flies rises during the day and falls during the night (3). Surprisingly, the TPR and locomotor activity are controlled through distinct circadian neurons(3). Drosophila locomotor activity is a well known circadian behavioral output and has provided strong contributions to the discovery of many conserved mammalian circadian clock genes and mechanisms(4). Therefore, understanding TPR will lead to the identification of hitherto unknown molecular and cellular circadian mechanisms. Here, we describe how to perform and analyze the TPR assay. This technique not only allows for dissecting the molecular and neural mechanisms of TPR, but also provides new insights into the fundamental mechanisms of the brain functions that integrate different environmental signals and regulate animal behaviors. Furthermore, our recently published data suggest that the fly TPR shares features with the mammalian BTR(3). Drosophila are ectotherms, in which the body temperature is typically behaviorally regulated. Therefore, TPR is a strategy used to generate a rhythmic body temperature in these flies(5-8). We believe that further exploration of Drosophila TPR will facilitate the characterization of the mechanisms underlying body temperature control in animals. PMID:24457268

Goda, Tadahiro; Leslie, Jennifer R; Hamada, Fumika N

2014-01-01

155

Circadian rhythms of gastrointestinal function are regulated by both central and peripheral oscillators  

PubMed Central

Circadian clocks are responsible for daily rhythms in a wide array of processes, including gastrointestinal (GI) function. These are vital for normal digestive rhythms and overall health. Previous studies demonstrated circadian clocks within the cells of GI tissue. The present study examines the roles played by the suprachiasmatic nuclei (SCN), master circadian pacemaker for overt circadian rhythms, and the sympathetic nervous system in regulation of circadian GI rhythms in the mouse Mus musculus. Surgical ablation of the SCN abolishes circadian locomotor, feeding, and stool output rhythms when animals are presented with food ad libitum, while restricted feeding reestablishes these rhythms temporarily. In intact mice, chemical sympathectomy with 6-hydroxydopamine has no effect on feeding and locomotor rhythmicity in light-dark cycles or constant darkness but attenuates stool weight and stool number rhythms. Again, however, restricted feeding reestablishes rhythms in locomotor activity, feeding, and stool output rhythms. Ex vivo, intestinal tissue from PER2::LUC transgenic mice expresses circadian rhythms of luciferase bioluminescence. Chemical sympathectomy has little effect on these rhythms, but timed administration of the ?-adrenergic agonist isoproterenol causes a phase-dependent shift in PERIOD2 expression rhythms. Collectively, the data suggest that the SCN are required to maintain feeding, locomotor, and stool output rhythms during ad libitum conditions, acting at least in part through daily activation of sympathetic activity. Even so, this input is not necessary for entrainment to timed feeding, which may be the province of oscillators within the intestines themselves or other components of the GI system. PMID:22723262

Malloy, Jaclyn N.; Paulose, Jiffin K.; Li, Ye

2012-01-01

156

Circadian rhythms from flies to human  

Microsoft Academic Search

In this era of jet travel, our body 'remembers' the previous time zone, such that when we travel, our sleep–wake pattern, mental alertness, eating habits and many other physiological processes temporarily suffer the consequences of time displacement until we adjust to the new time zone. Although the existence of a circadian clock in humans had been postulated for decades, an

Satchidananda Panda; John B. Hogenesch; Steve A. Kay

2002-01-01

157

CIRCADIAN RHYTHMS Chronobiology--Reducing Time  

NSDL National Science Digital Library

The authors provide perspective on two papers from the McKnight group, on pages 506 (2) and 510 (3) of this issue, which report on a fascinating discovery that may provide an unexpected molecular link between circadian oscillations and energy homeostasis.

Ueli Schibler (University of Geneva; Department of Molecular Biology, Sciences II)

2001-07-05

158

Characterization of locomotor activity circadian rhythms in athymic nude mice  

PubMed Central

Background The relation between circadian dysregulation and cancer incidence and progression has become a topic of major interest over the last decade. Also, circadian timing has gained attention regarding the use of chronopharmacology-based therapeutics. Given its lack of functional T lymphocytes, due to a failure in thymus development, mice carrying the Foxn1(?/?) mutation (nude mice) have been traditionally used in studies including implantation of xenogeneic tumors. Since the immune system is able to modulate the circadian clock, we investigated if there were alterations in the circadian system of the athymic mutant mice. Methods General activity circadian rhythms in 2–4 month-old Foxn1(?/?) mice (from Swiss Webster background) and their corresponding wild type (WT) controls was recorded. The response of the circadian system to different manipulations (constant darkness, light pulses and shifts in the light–dark schedule) was analyzed. Results Free-running periods of athymic mice and their wild type counterpart were 23.86?±?0.03 and 23.88?±?0.05 hours, respectively. Both strains showed similar phase delays in response to 10 or 120 minutes light pulses applied in the early subjective night and did not differ in the number of c-Fos-expressing cells in the suprachiasmatic nuclei, after a light pulse at circadian time (CT) 15. Similarly, the two groups showed no significant difference in the time needed for resynchronization after 6-hour delays or advances in the light–dark schedule. The proportion of diurnal activity, phase-angle with the zeitgeber, subjective night duration and other activity patterns were similar between the groups. Conclusions Since athymic Foxn1(?/?) mice presented no differences with the WT controls in the response of the circadian system to the experimental manipulations performed in this work, we conclude that they represent a good model in studies that combine xenograft implants with either alteration of the circadian schedules or chronopharmacological approaches to therapeutics. PMID:23369611

2013-01-01

159

KaiC CII Ring Flexibility Governs the Rhythm of the Circadian Clock of Cyanobacteria  

E-print Network

The circadian clock orchestrates metabolism and cell division and imposes important consequences to health and diseases, such as obesity, diabetes, and cancer. It is well established that phosphorylation-dependent circadian rhythms are the result...

Kuo, Nai-Wei

2012-07-16

160

Sex Differences in Behavioral Circadian Rhythms in Laboratory Rodents  

PubMed Central

There is a strong bias in basic research on circadian rhythms toward the use of only male animals in studies. Furthermore, of the studies that use female subjects, many use only females and do not compare results between males and females. This review focuses on behavioral aspects of circadian rhythms that differ between the sexes. Differences exist in the timing of daily onset of activity, responses to both photic and non-photic stimuli, and in changes across the lifespan. These differences may reflect biologically important traits that are ecologically relevant and impact on a variety of responses to behavioral and physiological challenges. Overall, more work needs to be done to investigate differences between males and females as well as differences that are the result of hormonal changes across the lifespan. PMID:25620955

Krizo, Jessica A.; Mintz, Eric M.

2014-01-01

161

Constitutive Expression of the CIRCADIAN CLOCK ASSOCIATED 1 ( CCA1) Gene Disrupts Circadian Rhythms and Suppresses Its Own Expression  

Microsoft Academic Search

The CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) gene encodes a MYB-related transcription factor involved in the phytochrome induction of a light-harvesting chlorophyll a\\/b-protein (Lhcb) gene. Expression of the CCA1 gene is transiently induced by phytochrome and oscillates with a circadian rhythm. Constitutive expression of CCA1 protein in transgenic plants abolished the circadian rhythm of several genes with dramatically different phases. These

Zhi-Yong Wang; Elaine M. Tobin

1998-01-01

162

Circadian rhythms of locomotor activity in naked mole-rats ( Heterocephalus glaber)  

Microsoft Academic Search

A wide variety of organisms exhibit various circadian rhythms in their behavior and physiology. Circadian rhythms are regulated by internal clocks that are generally entrained primarily by the environmental light:dark (L:D) cycle. There have been few studies of circadian rhythms in fossorial species that inhabit an environment where day–night variations are minimal and where exposure to light occurs infrequently. In

Alexandra P Riccio; Bruce D Goldman

2000-01-01

163

Jean-Jacques d'Ortous de Mairan, 1729 Circadian rhythms  

E-print Network

#12;Jean-Jacques d'Ortous de Mairan, 1729 #12;Circadian rhythms (David Dolezel - BCAV CR) david;#12;#12;#12;#12;#12;#12;#12;#12;#12;Circadian rhythms (David Dolezel - BCAV CR) david.dolezel@entu.cas.cz If you are here #12;#12;You are here large dose) at 8pm resulted in a normalization of his circadian rhythms within a month. The patient

South Bohemia, University of

164

Links between Circadian Rhythms and Psychiatric Disease  

PubMed Central

Determining the cause of psychiatric disorders is a goal of modern neuroscience, and will hopefully lead to the discovery of treatments to either prevent or alleviate the suffering caused by these diseases. One roadblock to attaining this goal is the realization that neuropsychiatric diseases are rarely due to a single gene polymorphism, environmental exposure, or developmental insult. Rather, it is a complex interaction between these various influences that likely leads to the development of clinically relevant syndromes. Our lab is exploring the links between environmental exposures and neurobehavioral function by investigating how disruption of the circadian (daily) clock alters the structure and function of neural circuits, with the hypothesis that disrupting this crucial homeostatic system can directly contribute to altered vulnerability of the organism to other factors that interact to produce psychiatric illness. This review explores some historical and more recent findings that link disrupted circadian clocks to neuropsychiatric disorders, particularly depression, mania, and schizophrenia. We take a comparative approach by exploring the effects observed in human populations, as well as some experimental models used in the laboratory to unravel mechanistic and causal relationships between disruption of the circadian clock and behavioral abnormalities. This is a rich area of research that we predict will contribute greatly to our understanding of how genes, environment, and development interact to modulate an individual’s vulnerability to psychiatric disorders. PMID:24834040

Karatsoreos, Ilia N.

2014-01-01

165

Studying circadian rhythm and sleep using genetic screens in Drosophila.  

PubMed

The power of Drosophila melanogaster as a model organism lies in its ability to be used for large-scale genetic screens with the capacity to uncover the genetic basis of biological processes. In particular, genetic screens for circadian behavior, which have been performed since 1971, allowed researchers to make groundbreaking discoveries on multiple levels: they discovered that there is a genetic basis for circadian behavior, they identified the so-called core clock genes that govern this process, and they started to paint a detailed picture of the molecular functions of these clock genes and their encoded proteins. Since the discovery that fruit flies sleep in 2000, researchers have successfully been using genetic screening to elucidate the many questions surrounding this basic animal behavior. In this chapter, we briefly recall the history of circadian rhythm and sleep screens and then move on to describe techniques currently employed for mutagenesis and genetic screening in the field. The emphasis lies on comparing the newer approaches of transgenic RNA interference (RNAi) to classical forms of mutagenesis, in particular in their application to circadian behavior and sleep. We discuss the different screening approaches in light of the literature and published and unpublished sleep and rhythm screens utilizing ethyl methanesulfonate mutagenesis and transgenic RNAi from our lab. PMID:25662449

Axelrod, Sofia; Saez, Lino; Young, Michael W

2015-01-01

166

Neuromedin s-producing neurons act as essential pacemakers in the suprachiasmatic nucleus to couple clock neurons and dictate circadian rhythms.  

PubMed

Circadian behavior in mammals is orchestrated by neurons within the suprachiasmatic nucleus (SCN), yet the neuronal population necessary for the generation of timekeeping remains unknown. We show that a subset of SCN neurons expressing the neuropeptide neuromedin S (NMS) plays an essential role in the generation of daily rhythms in behavior. We demonstrate that lengthening period within Nms neurons is sufficient to lengthen period of the SCN and behavioral circadian rhythms. Conversely, mice without a functional molecular clock within Nms neurons lack synchronous molecular oscillations and coherent behavioral daily rhythms. Interestingly, we found that mice lacking Nms and its closely related paralog, Nmu, do not lose in vivo circadian rhythms. However, blocking vesicular transmission from Nms neurons with intact cell-autonomous clocks disrupts the timing mechanisms of the SCN, revealing that Nms neurons define a subpopulation of pacemakers that control SCN network synchrony and in vivo circadian rhythms through intercellular synaptic transmission. PMID:25741729

Lee, Ivan T; Chang, Alexander S; Manandhar, Manabu; Shan, Yongli; Fan, Junmei; Izumo, Mariko; Ikeda, Yuichi; Motoike, Toshiyuki; Dixon, Shelley; Seinfeld, Jeffrey E; Takahashi, Joseph S; Yanagisawa, Masashi

2015-03-01

167

Circadian rhythm dissociation in an environment with conflicting temporal information  

NASA Technical Reports Server (NTRS)

The relative contributions of light-dark (LD) cycles and eating-fasting (EF) cycles in providing temporal information to the circadian time-keeping system were examined in chair-acclimatized squirrel monkeys (Saimiri sciureus). The circadian rhythms of drinking, colonic temperature, urine volume, and urinary potassium excretion were measured with the LD and EF cycles providing either conflicting phases or periods. In conflicting phase experiments, animals were exposed to 24-hr LD cycles consisting of 12 hr of 600 lx followed by 12 hr of less than 1 lx and concurrent 24-hr EF cycles in which the animals ate for 3 hr and then fasted for 21 hr. One group had food available at the beginning and a second group at the end of the light period. In conflicting period experiments, monkeys were exposed to 23-hr LD cycles and 24-hr EF cycles. Analysis of the rhythms showed that both phase and period information were conveyed to the drinking and urinary rhythms by the EF cycle, and to the temperature rhythm by the LD cycle.

Sulzman, F. M.; Fuller, C. A.; Hiles, L. G.; Moore-Ede, M. C.

1978-01-01

168

cap alpha. -Methyl-p-tyrosine shifts circadian temperature rhythms  

SciTech Connect

..cap alpha..-Methyl-p-tyrosine shifts the acrophase (time of highest temperature) of the circadian temperature rhythm of the rat to earlier or later times of day depending on the phase of the cicadian cycle at which the drug is administered. When ..cap alpha..-methyl-p-tyrosine methyl ester HCl is injected intraperitoneally at a dose of 100 mg/kg late in the projected 8-h light phase, the acrophase of the intraperitoneal temperature rhythm is delayed by up to 3 h.However, when the same dose of drug is given 9-10 h into the projected 16-h dark phase of the daily cycle, the acrophase of the temperature rhythm occurs about 2 h earlier than expected. The times of ..cap alpha..-methyl-p-tyrosine administration leading to maximal phase delays or advances are correlated with the times of minimal and maximal turnover of norepinephrine in the hypothalamus. These results suggest that changing rates of norepinephrine turnover in the hypothalamus may regulate the circadian temperature rhythm in rats. The results also emphasize the fact that the effects of drugs may vary as a function of the time of administration. This fact must be taken into account in pharmacologic testing.

Cahill, A.L.; Ehret, C.F.

1982-09-01

169

Therapeutic implications of circadian rhythms in cancer patients.  

PubMed

Drug absorption, transport, metabolism and/or elimination usually show 24 h changes in both laboratory rodents and human beings. These variations in target cell exposure to drugs, as well as the rhythms which modulate cellular detoxification functions, account for the chronopharmacology of most medications, including anticancer agents, and have warranted the exploration of the relevance of the chronotherapy principle. Most of the cellular detoxication rhythms appear to be coupled to the rest-activity cycle, both in nocturnally active rodents and in diurnally active healthy subjects as well as in cancer patients. For instance, a 24 h rhythm was found in the activity of dehydropyrimidine dehydrogenase (DPD), both in rodent liver and in human circulating mononuclear cells, with a maximum located in the early rest span in either species. This cellular enzyme catabolizes 5-fluorouracil (5-FU), hence protects normal cells against damage produced by this widely used antimetabolite drug. Although DPD amplitude was nearly threefold in rodent liver and 40% in human lymphocytes, the adaptation of 5-FU administration to this rhythm largely improved tolerability both in rodents and in patients. The results thus support the coupling of the DPD rhythm and other chronopharmacology mechanisms to the average rest-activity cycle across species. The clinical relevance of such group chronotherapy has been further validated in Phase I, II and III clinical trials involving nearly 1500 patients. Multicentre randomized clinical trials have demonstrated that chronotherapy was both better tolerated and more effective than constant rate infusion in patients with metastatic colorectal cancer. Nevertheless 24 h rhythms in plasma cortisol or rest-activity could be altered in nearly 30% of cancer patients. Results from a prospective study performed in 200 patients with metastatic colorectal cancer indicated that poor circadian coordination constitutes an independent prognostic factor of both treatment tolerability and efficacy. Novel chronotherapeutic approaches targeted at circadian system coordination should then be devised in these patients. PMID:10752068

Lévi, F

2000-01-01

170

Circadian activity rhythms and mortality: the Study of Osteoporotic Fractures  

PubMed Central

OBJECTIVES To determine whether circadian activity rhythms are associated with mortality in community-dwelling older women. DESIGN Prospective study of mortality. SETTING A cohort study of health and aging. PARTICIPANTS 3,027 community-dwelling women from the Study of Osteoporotic Fractures cohort (mean age 84 years). MEASUREMENTS Activity data were collected with wrist actigraphy for a minimum of three 24-hour periods and circadian activity rhythms were computed. Parameters of interest included height of activity peak (amplitude), mean activity level (mesor), strength of activity rhythm (robustness), and time of peak activity (acrophase). Vital status, with cause of death adjudicated through death certificates, was prospectively ascertained. RESULTS Over an average of 4.1 years of follow-up there were 444 (15%) deaths. There was an inverse association between peak activity height and all-cause mortality rates with higher mortality rates observed in the lowest activity quartile (Hazard ratio [HR]=2.18, 95% CI, 1.63–2.92) compared with the highest quartile after adjusting for age, clinic site, race, BMI, cognitive function, exercise, IADL impairments, depression, medications, alcohol, smoking, self-reported health status, married status, and co-morbidities. Increased risk of all-cause mortality was observed between lower mean activity level (HR=1.71, 95% CI, 1.29–2.27) and rhythm robustness (HR=1.97, 95% CI, 1.50–2.60). Increased mortality from cancer (HR=2.09, 95% CI, 1.04–4.22) and stroke (HR=2.64, 95% CI, 1.11–6.30) was observed for a delayed timing of peak activity (after 4:33PM; >1.5 SD from mean) when compared to the mean peak range (2:50PM–4:33PM). CONCLUSION Older women with weak circadian activity rhythms have higher mortality risk. If confirmed in other cohorts, studies will be needed to test whether interventions (e.g. physical activity, bright light exposure) that regulate circadian activity rhythms will improve health outcomes in the elderly. PMID:20374404

Tranah, Gregory J.; Blackwell, Terri; Ancoli-Israel, Sonia; Paudel, Misti L.; Ensrud, Kristine E.; Cauley, Jane A.; Redline, Susan; Hillier, Teresa A.; Cummings, Steven R; Stone, Katie L.

2010-01-01

171

Implicit Associations Have a Circadian Rhythm  

PubMed Central

The current study shows that people's ability to inhibit implicit associations that run counter to their explicit views varies in a circadian pattern. The presence of this rhythmic variation suggests the involvement of a biological process in regulating automatic associations—specifically, with the current data, associations that form undesirable social biases. In 1998, Greenwald, McGhee, and Schwartz introduced the Implicit Association Test as a means of measuring individual differences in implicit cognition. The IAT is a powerful tool that has become widely used. Perhaps most visibly, studies employing the IAT demonstrate that people generally hold implicit biases against social groups, which often conflict with their explicitly held views. The IAT engages inhibitory processes similar to those inherent in self-control tasks. Because the latter processes are known to be resource-limited, we considered whether IAT scores might likewise be resource dependent. Analyzing IAT performance from over a million participants across all times of day, we found a clear circadian pattern in scores. This finding suggests that the IAT measures not only the strength of implicit associations, but also the effect of variations in the physiological resources available to inhibit their undesirable influences on explicit behavior. PMID:25365254

Zadra, Jonathan R.; Proffitt, Dennis R.

2014-01-01

172

Respiratory Rhythm Generation In Vivo  

PubMed Central

The cellular and circuit mechanisms generating the rhythm of breathing in mammals have been under intense investigation for decades. Here, we try to integrate the key discoveries into an updated description of the basic neural processes generating respiratory rhythm under in vivo conditions. PMID:24382872

Richter, Diethelm W.; Smith, Jeffrey C.

2014-01-01

173

Independence of genetic variation between circadian rhythm and development time in the seed beetle, Callosobruchus chinensis.  

PubMed

A positive genetic correlation between periods of circadian rhythm and developmental time supports the hypothesis that circadian clocks are implicated in the timing of development. Empirical evidence for this genetic correlation in insects has been documented in two fly species. In contrast, here we show that there is no evidence of genetic correlation between circadian rhythm and development time in the adzuki bean beetle, Callosobruchus chinensis. This species has variation that is explained by a major gene in the expression and period length of circadian rhythm between strains. In this study, we found genetic variation in development time between the strains. The development time was not covaried with either the incidence or the period length of circadian rhythm among the strains. Crosses between strains suggest that development time is controlled by a polygene. In the F(2) individuals from the crosses, the circadian rhythm is attributable to allelic variation in the major gene. Across the F(2) individuals, development time was not correlated with either the expression or the period length of circadian rhythm. Thus, we found no effects of major genes responsible for variation in the circadian rhythm on development time in C. chinensis. Our findings collectively give no support to the hypothesis that the circadian clock is involved in the regulation of development time in this species. PMID:21211539

Harano, Tomohiro; Miyatake, Takahisa

2011-03-01

174

Neonatal monosodium glutamate treatment prevents effects of constant light on circadian temperature rhythms of adult rats  

Microsoft Academic Search

Housing rats under continuous illumination (LL) disrupts circadian rhythms controlled by a pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). The neural mechanisms underlying this effect are not well understood. The present study examined the effects of LL on circadian rhythms and on light-induced expression of Fos protein in the SCN, intergeniculate leaflet (IGL), and ventrolateral geniculate nucleus (vLGN) in

K. Edelstein; J. G. Pfaus; B. Rusak; S. Amir

1995-01-01

175

Circadian rhythms in myocardial metabolism and contractile function; influence of workload and oleate  

Technology Transfer Automated Retrieval System (TEKTRAN)

Multiple extra-cardiac stimuli, such as workload and circulating nutrients (e.g., fatty acids), known to influence myocardial metabolism and contractile function exhibit marked circadian rhythms. The aim of the present study was to investigate whether the rat heart exhibits circadian rhythms in its ...

176

POTENTIATION OF THE RESETTING EFFECTS OF LIGHT ON CIRCADIAN RHYTHMS OF HAMSTERS USING SEROTONIN  

E-print Network

entrainment signal; how- ever, non-photic cues, such as sleep deprivation or exer- cise, also influencePOTENTIATION OF THE RESETTING EFFECTS OF LIGHT ON CIRCADIAN RHYTHMS OF HAMSTERS USING SEROTONIN. In hamsters, the effects of light on circadian rhythms can be modulated by serotonergic input

Harrington, Mary

177

Individual neurons dissociated from rat suprachiasmatic nucleus express independently phased circadian firing rhythms  

Microsoft Academic Search

Within the mammalian hypothalamus, the suprachiasmatic nucleus (SCN) contains a circadian clock for timing of diverse neuronal, endocrine, and behavioral rhythms. By culturing cells from neonatal rat SCN on fixed microelectrode arrays, we have been able to record spontaneous action potentials from individual SCN neurons for days or weeks, revealing prominent circadian rhythms in firing rate. Despite abundant functional synapses,

David K. Welsh; Diomedes E. Logothetis; Markus Meister; Steven M. Reppert

1995-01-01

178

Circadian rhythms in a long-term duration space flight  

NASA Astrophysics Data System (ADS)

In order to maintain cosmonaut health and performance, it is important for the work-rest schedule to follow human circadian rhythms (CR). What happens with CR in space flight? Investigations of CR in mammals revealed, that the circadian phase in flight is less stable, probably due to a displacement of the range of entrainment, resulting from internal period change (the latter was confirmed on insects). The circadian period may be a gravity-dependent parameter. If so, the basic biological requirement for the day length might be different in weightlessness. On this basis, a higher risk of desynchronosis is expected in a long-duration space flight. As a countermeasure, a non-24-hr day length could be suggested, being close to the internal circadian period (in humans about 25 hr). Taking into account a possible displacement of period in weightlessness, it seems reasonable to establish a flexible work-rest schedule, capable to follow the body temperature CR by means of biofeedback.

Alpatov, Alexey M.

179

Comparison of circadian rhythms in male and female humans  

NASA Technical Reports Server (NTRS)

Heart rate (HR) and rectal temperature (RT) data were obtained from 12 female and 27 male subjects. The subjects were housed in a facility where the environment was controlled. Human male and female RT and HR exhibit a circadian rhythm with an excursion of about 1.2 C and 30 beats/min, respectively. The acrophases, amplitudes, and level crossings are only slightly different between the sexes. The male HR and RT circadian wave forms are more stable than those of the females. However, the actual RT and HR of males were always lower than that of females at all time points around the clock. The HR during sleep in females is 15 per cent below the daily mean heart rate and in males, 22 per cent.

Winget, C. M.; Deroshia, C. W.; Vernikos-Danellis, J.; Rosenblatt, W. S.; Hetherington, N. W.

1977-01-01

180

Period doubling observed in the circadian photosynthetic rhythm of the prokaryotic cyanobacterium Cyanothece RF-1  

NASA Astrophysics Data System (ADS)

The circadian rhythm is an endogenous biological clock that governs biochemical phenomena or behavior in organisms. The Cyanothece RF-1 is the first prokaryote shown to exhibit circadian nitrogen-fixing rhythm. The observation of the circadian photosynthetic rhythm of this strain was recently reported by the authors. In this work, the dissolved-oxygen variation in the culture of Cyanothece RF-1 was recorded, which would reveal the photosynthetic activity of the strain. For a culture of about 1x10^8 cells/ml in concentration, a period-doubling pattern was clearly displayed in the circadian photosynthetic rhythm signals. The mechanism corresponding to this nonlinear effect will be discussed. These results represent the first observation of the period doubling in the circadian rhythm of a prokaryotic cyanobacterium.

Yen, Tsu-Chiang; Cheng, Da-Long

2005-03-01

181

Aging human circadian rhythms: conventional wisdom may not always be right  

NASA Technical Reports Server (NTRS)

This review discusses the ways in which the circadian rhythms of older people are different from those of younger adults. After a brief discussion of clinical issues, the review describes the conventional wisdom regarding age-related changes in circadian rhythms. These can be summarized as four assertions regarding what happens to people as they get older: 1) the amplitude of their circadian rhythms reduces, 2) the phase of their circadian rhythms becomes earlier, 3) their natural free-running period (tau) shortens, and 4) their ability to tolerate abrupt phase shifts (e.g., from jet travel or night work) worsens. The review then discusses the empirical evidence for and against these assertions and discusses some alternative explanations. The conclusions are that although older people undoubtedly have earlier circadian phases than younger adults, and have more trouble coping with shift work and jet lag, evidence for the assertions about rhythm amplitude and tau are, at best, mixed.

Monk, Timothy H.

2005-01-01

182

Circadian Rhythms in Gene Expression: Relationship to Physiology, Disease, Drug Disposition and Drug Action  

PubMed Central

Circadian rhythms (24 h cycles) are observed in virtually all aspects of mammalian function from expression of genes to complex physiological processes. The master clock is present in the suprachiasmatic nucleus (SCN) in the anterior part of the hypothalamus and controls peripheral clocks present in other parts of the body. Components of this core clock mechanism regulate the circadian rhythms in genome-wide mRNA expression, which in turn regulate various biological processes. Disruption of circadian rhythms can be either the cause or the effect of various disorders including metabolic syndrome, inflammatory diseases and cancer. Furthermore, circadian rhythms in gene expression regulate both the action and disposition of various drugs and affect therapeutic efficacy and toxicity based on dosing time. Understanding the regulation of circadian rhythms in gene expression plays an important role in both optimizing the dosing time for existing drugs and in development of new therapeutics targeting the molecular clock. PMID:20542067

Sukumaran, Siddharth; Almon, Richard R.; DuBois, Debra C.; Jusko, William J.

2010-01-01

183

Sleep deprivation and circadian rhythm in depression.  

PubMed

The effect of total sleep deprivation for one night on the depressive state (measured using the depression rating scale of Bojanovsky and Chloupkova) and the patients' actual state of well being (measured using the self-rating scale of von Zerssen) is investigated in a group of 40 randomly selected inpatient depressives (29 endogenous depressives, 11 neurotic depressives) over a period of 36 h. The endogenous depressives exhibited a statistically significant change. The total index of the depression scale improved by 22.6%, recorded as a 'daily mean difference'. The individual symptoms of depressive mood, lack of interest, inhibition and inappetence were significantly improved. The feature of vital disorders and its common appearance with diurnal variations correlates positively with the degree of sleep deprivation effect. The symptomatology of the neurotic depressive patients also showed a significant improvement but the relatively small group of particularly severe neurotic depressives who also exhibited vital disorders is not representative. In a group of cases, sleep deprivation caused reversion in the depressive symptomatology not only during the night of deprivation but influenced the diurnal rhythm of the depressive symptomatology on the following day, in a therapeutically favourable direction. The results are compared with those of other studies. The methodological problems are discussed and methodological improvements for further investigation are proposed. PMID:572080

Rudolf, G A; Tölle, R

1978-01-01

184

Role of Melatonin in the Regulation of Human Circadian Rhythms and Sleep  

Microsoft Academic Search

Abstract The circadian rhythm,of pineal melatonin,is the best marker,of internal time under low ambient,light levels. The endogenous,melatonin,rhythm,exhibits a close association with the endogenous,circadian component,of the sleep propensity rhythm. This has led to the idea that melatonin is an internal sleep ‘facilitator’ in humans, and,therefore useful in the treatment,of insomnia,and the readjustment,of circadian rhythms. There is evidence,that administration of melatonin,is able:

C. Cajochen; K. Kra Uchi; A. Wirz-justice

185

Aging, circadian rhythms and depressive disorders: a review  

PubMed Central

Introduction: Aging is typically associated with impairing behavioral patterns that are frequently and inappropriately seen as normal. Circadian rhythm changes and depressive disorders have been increasingly proposed as the two main overlapping and interpenetrating changes that take place in older age. This study aims to review the state of the art on the subject concerning epidemiology, pathophysiological mechanism, clinical findings and relevance, as well as available treatment options. Materials and Methods: A nonsystematic review of all English language PubMed articles published between 1995 and December 2012 using the terms “circadian rhythms”, “mood disorders”, “depression”, “age”, “aging”, “elderly” and “sleep”. Discussion and conclusion: Sleep disorders, mainly insomnia, and depression have been demonstrated to be highly co-prevalent and mutually precipitating conditions in the elderly population. There is extensive research on the pathophysiological mechanisms through which age conditions circadian disruption, being the disruption of the Melatonin system one of the main changes. However, research linking clearly and unequivocally circadian disruption and mood disorders is still lacking. Nonetheless, there are consistently described molecular changes on shared genes and also several proposed pathophysiological models linking depression and sleep disruption, with clinical studies also suggesting a bi-directional relationship between these pathologies. In spite of this suggested relation, clinical evaluation of these conditions in elderly patients consistently reveals itself rather complicated due to the frequently co-existing co-morbidities, some of them having been demonstrated to alter sleep and mood patters. This is the case of strokes, forms of dementia such as Alzheimer and Parkinson, several neurodegenerative disorders, among others. Although there are to the present no specific treatment guidelines, available treatment options generally base themselves on the premise that depression and sleep disturbances share a bidirectional relationship and so, the adoption of measures that address specifically one of the conditions will reciprocally benefit the other. Treatment options range from Cognitive Behavioral Therapy, Chronotherapy, and Light therapy, to drugs such as Melatonin/Melatonin agonists, antidepressants and sedatives. PMID:24319642

Campos Costa, Inês; Nogueira Carvalho, Hugo; Fernandes, Lia

2013-01-01

186

Circadian rhythm disorders among adolescents: assessment and treatment options.  

PubMed

Delayed sleep phase disorder (DSPD) - a circadian rhythm sleep disorder - is most commonly seen in adolescents. The differential diagnosis between DSPD and conventional psychophysiological insomnia is important for correct therapeutic intervention. Adolescent DSPD sleep duration is commonly 9 hours or more. Depression may be comorbid with DSPD. DSPD has a negative impact on adolescent academic performance. DSPD treatments include bright light therapy, chronotherapeutic regimens, and administration of melatonin as a chronobiotic (as distinct from a soporific). Attention to non-photic and extrinsic factors including healthy sleep parameters is also important to enable better sleep and mood outcomes in adolescents. PMID:24138360

Bartlett, Delwyn J; Biggs, Sarah N; Armstrong, Stuart M

2013-10-21

187

CIRCADIAN RHYTHMS IN PLANTS: MA-CHINE LEARNING MODELS AND BIOIN-  

E-print Network

TH E U N I V E R S ITY OF E D I N B U R G H CIRCADIAN RHYTHMS IN PLANTS: MA- CHINE LEARNING MODELS.trejo-banos@sms.ed.ac.uk http://www.inf.ed.ac.uk/people/students/Daniel_Trejo_Banos.html Introduction Circadian Rhythms (temperature compensated)[1]. The molecular basis of the circadian oscillator is currently described as many

Chaudhuri, Surajit

188

A neural theory of circadian rhythms: Aschoff s rule in diurnal and nocturnal mammals  

E-print Network

"" , - , ,\\i', (-\\' A neural theory of circadian rhythms: Aschoff s rule in diurnal and nocturnal- theory of circadian rhythms: A~choff's rule in diurnal and nr:c- mals, including the "dead zone" of phase.lcnuclelsuggest~h°v.:beha":lor~lac~lvIty,rest, of the pacemaker by high light intensities (3,11). Due to and circadian period depend on light intensity In diurnal

Grossberg, Stephen

189

Experiment K-7-35: Circadian Rhythms and Temperature Regulation During Spaceflight. Part 1; Circadian Rhythms and Temperature Regulation  

NASA Technical Reports Server (NTRS)

Mammals have developed the ability to adapt to most variations encountered in their everyday environment. For example, homeotherms have developed the ability to maintain the internal cellular environment at a relatively constant temperature. Also, in order to compensate for temporal variations in the terrestrial environment, the circadian timing system has evolved. However, throughout the evolution of life on earth, living organisms have been exposed to the influence of an unvarying level of earth's gravity. As a result changes in gravity produce adaptive responses which are not completely understood. In particular, spaceflight has pronounced effects on various physiological and behavioral systems. Such systems include body temperature regulation and circadian rhythms. This program has examined the influence of microgravity on temperature regulation and circadian timekeeping systems in Rhesus monkeys. Animals flown on the Soviet Biosatellite, COSMOS 2044, were exposed to 14 days of microgravity while constantly monitoring the circadian patterns temperature regulation, heart rate and activity. This experiment has extended our previous observations from COSMOS 1514, as well as providing insights into the physiological mechanisms that produce these changes.

Fuller, C. A.; Alpatov, A. M.; Hoban-Higgins, T. M.; Klimovitsky, V. Y.

1994-01-01

190

Differential Contribution of Rod and Cone Circadian Clocks in Driving Retinal Melatonin Rhythms in Xenopus  

PubMed Central

Background Although an endogenous circadian clock located in the retinal photoreceptor layer governs various physiological events including melatonin rhythms in Xenopus laevis, it remains unknown which of the photoreceptors, rod and/or cone, is responsible for the circadian regulation of melatonin release. Methodology/Principal Findings We selectively disrupted circadian clock function in either the rod or cone photoreceptor cells by generating transgenic Xenopus tadpoles expressing a dominant-negative CLOCK (XCL?Q) under the control of a rod or cone-specific promoter. Eyecup culture and continuous melatonin measurement revealed that circadian rhythms of melatonin release were abolished in a majority of the rod-specific XCL?Q transgenic tadpoles, although the percentage of arrhythmia was lower than that of transgenic tadpole eyes expressing XCL?Q in both rods and cones. In contrast, whereas a higher percentage of arrhythmia was observed in the eyes of the cone-specific XCL?Q transgenic tadpoles compare to wild-type counterparts, the rate was significantly lower than in rod-specific transgenics. The levels of the transgene expression were comparable between these two different types of transgenics. In addition, the average overall melatonin levels were not changed in the arrhythmic eyes, suggesting that CLOCK does not affect absolute levels of melatonin, only its temporal expression pattern. Conclusions/Significance These results suggest that although the Xenopus retina is made up of approximately equal numbers of rods and cones, the circadian clocks in the rod cells play a dominant role in driving circadian melatonin rhythmicity in the Xenopus retina, although some contribution of the clock in cone cells cannot be excluded. PMID:21187976

Hayasaka, Naoto; LaRue, Silvia I.; Green, Carla B.

2010-01-01

191

Isolation and phenogenetics of a novel circadian rhythm mutant in zebrafish.  

PubMed

Widespread use of zebrafish (Danio rerio) in genetic analysis of embryonic development has led to rapid advances in the technology required to generate, map and clone mutated genes. To identify genes involved in the generation and regulation of vertebrate circadian rhythmicity, we screened for dominant mutations that affect the circadian periodicity of larval zebrafish locomotor behavior. In a screen of 6,500 genomes, we recovered 8 homozygous viable, semi-dominant mutants, and describe one of them here. The circadian period of the lager and lime (lag(dg2)) mutant is shortened by 0.7 h in heterozygotes,and 1.3 h in homozygotes. This mutation also shortens the period of the melatonin production rhythm measured from cultured pineal glands, indicating that the mutant gene product affects circadian rhythmicity at the tissue level, as well as at the behavioral level. This mutation also alters the sensitivity of pineal circadian period to temperature, but does not affect phase shifting responses to light. Linkage mapping with microsatellite markers indicates that the lag mutation is on chromosome 7. A zebrafish homolog of period1(per1) is the only known clock gene homolog that maps near the lag locus. However, all sequence variants found in per1 cDNA from lag(dg2) mutants are also present in wild type lines, and we were unable to detect any defect in per1 mRNA splicing, so this mutation may identify a novel clock gene. PMID:15763996

DeBruyne, Jason; Hurd, Mark W; Gutiérrez, Laura; Kaneko, Maki; Tan, Ying; Wells, Dan E; Cahill, Gregory M

2004-01-01

192

Thoracic surface temperature rhythms as circadian biomarkers for cancer chronotherapy  

PubMed Central

The disruption of the temperature circadian rhythm has been associated with cancer progression, while its amplification resulted in cancer inhibition in experimental tumor models. The current study investigated the relevance of skin surface temperature rhythms as biomarkers of the Circadian Timing System (CTS) in order to optimize chronotherapy timing in individual cancer patients. Baseline skin surface temperature at four sites and wrist accelerations were measured every minute for 4 days in 16 patients with metastatic gastro-intestinal cancer before chronotherapy administration. Temperature and rest-activity were recorded, respectively, with wireless skin surface temperature patches (Respironics, Phillips) and an actigraph (Ambulatory Monitoring). Both variables were further monitored in 10 of these patients during and after a 4-day course of a fixed chronotherapy protocol. Collected at baseline, during and after therapy longitudinal data sets were processed using Fast Fourier Transform Cosinor and Linear Discriminant Analyses methods. A circadian rhythm was statistically validated with a period of 24 h (p<0.05) for 49/61 temperature time series (80.3%), and 15/16 rest-activity patterns (93.7%) at baseline. However, individual circadian amplitudes varied from 0.04 °C to 2.86 °C for skin surface temperature (median, 0.72 °C), and from 16.6 to 146.1 acc/min for rest-activity (median, 88.9 acc/min). Thirty-nine pairs of baseline temperature and rest-activity time series (75%) were correlated (r>|0.7|; p<0.05). Individual circadian acrophases at baseline were scattered from 15:18 to 6:05 for skin surface temperature, and from 12:19 to 15:18 for rest-activity, with respective median values of 01:10 (25–75% quartiles, 22:35–3:07) and 14:12 (13:14–14:31). The circadian patterns in skin surface temperature and rest-activity persisted or were amplified during and after fixed chronotherapy delivery for 5/10 patients. In contrast, transient or sustained disruption of these biomarkers was found for the five other patients, as indicated by the lack of any statistically significant dominant period in the circadian range. No consistent correlation (r<|0.7|, p ? 0.05) was found between paired rest-activity and temperature time series during fixed chronotherapy delivery. In conclusion, large inter-patient differences in circadian amplitudes and acrophases of skin surface temperature were demonstrated for the first time in cancer patients, despite rather similar rest-activity acrophases. The patient-dependent coupling between both CTS biomarkers, and its possible alteration on a fixed chronotherapy protocol, support the concept of personalized cancer chronotherapy. PMID:24397341

Roche, Véronique Pasquale; Mohamad-Djafari, Ali; Innominato, Pasquale Fabio; Karaboué, Abdoulaye; Gorbach, Alexander; Lévi, Francis Albert

2014-01-01

193

Effect of circadian rhythm on CNS oxygen toxicity.  

NASA Technical Reports Server (NTRS)

The circadian rhythm in susceptibility to oxygen toxicity seizures was investigated by using six groups of 20 male Sprague-Dawley rats (101-196 gm.). The animals were given standard chow, exposed to standard diurnal conditions of light (0700-1900 hr) and dark (1900-0700 hr), and fasted for 15-16 hr prior to exposure to hyperbaric oxygen. The animals were placed in a previously oxygen flushed chamber and raised to 60 psi (gauge) oxygen at a rate of 3 psi/min. Time of exposure started with attainment of 60 psi. End point was first convulsion. The animals' weights were equally distributed within the groups, and the groups were defined by hour of exposure. Time of exposure in minutes prior to seizure was significantly longer in those exposed at 0700-0800 hr and 1000-1100 hr than in four other groups. There was no relationship between animals' weights and time of exposure to seizures. All R values were negative, and the highest R value was -035. These data suggest a definite circadian rhythm in susceptibility to oxygen toxicity seizures.

Hof, D. G.; Dexter, J. D.; Mengel, C. E.

1971-01-01

194

Wavelet-based analysis of circadian behavioral rhythms.  

PubMed

The challenging problems presented by noisy biological oscillators have led to the development of a great variety of methods for accurately estimating rhythmic parameters such as period and amplitude. This chapter focuses on wavelet-based methods, which can be quite effective for assessing how rhythms change over time, particularly if time series are at least a week in length. These methods can offer alternative views to complement more traditional methods of evaluating behavioral records. The analytic wavelet transform can estimate the instantaneous period and amplitude, as well as the phase of the rhythm at each time point, while the discrete wavelet transform can extract the circadian component of activity and measure the relative strength of that circadian component compared to those in other frequency bands. Wavelet transforms do not require the removal of noise or trend, and can, in fact, be effective at removing noise and trend from oscillatory time series. The Fourier periodogram and spectrogram are reviewed, followed by descriptions of the analytic and discrete wavelet transforms. Examples illustrate application of each method and their prior use in chronobiology is surveyed. Issues such as edge effects, frequency leakage, and implications of the uncertainty principle are also addressed. PMID:25662453

Leise, Tanya L

2015-01-01

195

Protecting the Melatonin Rhythm through Circadian Healthy Light Exposure  

PubMed Central

Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system. PMID:25526564

Bonmati-Carrion, Maria Angeles; Arguelles-Prieto, Raquel; Martinez-Madrid, Maria Jose; Reiter, Russel; Hardeland, Ruediger; Rol, Maria Angeles; Madrid, Juan Antonio

2014-01-01

196

Protecting the melatonin rhythm through circadian healthy light exposure.  

PubMed

Currently, in developed countries, nights are excessively illuminated (light at night), whereas daytime is mainly spent indoors, and thus people are exposed to much lower light intensities than under natural conditions. In spite of the positive impact of artificial light, we pay a price for the easy access to light during the night: disorganization of our circadian system or chronodisruption (CD), including perturbations in melatonin rhythm. Epidemiological studies show that CD is associated with an increased incidence of diabetes, obesity, heart disease, cognitive and affective impairment, premature aging and some types of cancer. Knowledge of retinal photoreceptors and the discovery of melanopsin in some ganglion cells demonstrate that light intensity, timing and spectrum must be considered to keep the biological clock properly entrained. Importantly, not all wavelengths of light are equally chronodisrupting. Blue light, which is particularly beneficial during the daytime, seems to be more disruptive at night, and induces the strongest melatonin inhibition. Nocturnal blue light exposure is currently increasing, due to the proliferation of energy-efficient lighting (LEDs) and electronic devices. Thus, the development of lighting systems that preserve the melatonin rhythm could reduce the health risks induced by chronodisruption. This review addresses the state of the art regarding the crosstalk between light and the circadian system. PMID:25526564

Bonmati-Carrion, Maria Angeles; Arguelles-Prieto, Raquel; Martinez-Madrid, Maria Jose; Reiter, Russel; Hardeland, Ruediger; Rol, Maria Angeles; Madrid, Juan Antonio

2014-01-01

197

Circadian Sleep-Wake Rhythm of Older Adults with Intellectual Disabilities  

ERIC Educational Resources Information Center

The circadian sleep-wake rhythm changes with aging, resulting in a more fragmented sleep-wake pattern. In individuals with intellectual disabilities (ID), brain structures regulating the sleep-wake rhythm might be affected. The aims of this study were to compare the sleep-wake rhythm of older adults with ID to that of older adults in the general…

Maaskant, Marijke; van de Wouw, Ellen; van Wijck, Ruud; Evenhuis, Heleen M.; Echteld, Michael A.

2013-01-01

198

Circadian rhythm phase shifts and endogenous free-running circadian period differ between African-Americans and European-Americans  

PubMed Central

Successful adaptation to modern civilization requires the internal circadian clock to make large phase shifts in response to circumstances (e.g., jet travel and shift work) that were not encountered during most of our evolution. We found that the magnitude and direction of the circadian clock's phase shift after the light/dark and sleep/wake/meal schedule was phase-advanced (made earlier) by 9?hours differed in European-Americans compared to African-Americans. European-Americans had larger phase shifts, but were more likely to phase-delay after the 9-hour advance (to phase shift in the wrong direction). The magnitude and direction of the phase shift was related to the free-running circadian period, and European-Americans had a longer circadian period than African-Americans. Circadian period was related to the percent Sub-Saharan African and European ancestry from DNA samples. We speculate that a short circadian period was advantageous during our evolution in Africa and lengthened with northern migrations out of Africa. The differences in circadian rhythms remaining today are relevant for understanding and treating the modern circadian-rhythm-based disorders which are due to a misalignment between the internal circadian rhythms and the times for sleep, work, school and meals. PMID:25670162

Eastman, Charmane I.; Suh, Christina; Tomaka, Victoria A.; Crowley, Stephanie J.

2015-01-01

199

Circadian rhythm phase shifts and endogenous free-running circadian period differ between African-Americans and European-Americans.  

PubMed

Successful adaptation to modern civilization requires the internal circadian clock to make large phase shifts in response to circumstances (e.g., jet travel and shift work) that were not encountered during most of our evolution. We found that the magnitude and direction of the circadian clock's phase shift after the light/dark and sleep/wake/meal schedule was phase-advanced (made earlier) by 9?hours differed in European-Americans compared to African-Americans. European-Americans had larger phase shifts, but were more likely to phase-delay after the 9-hour advance (to phase shift in the wrong direction). The magnitude and direction of the phase shift was related to the free-running circadian period, and European-Americans had a longer circadian period than African-Americans. Circadian period was related to the percent Sub-Saharan African and European ancestry from DNA samples. We speculate that a short circadian period was advantageous during our evolution in Africa and lengthened with northern migrations out of Africa. The differences in circadian rhythms remaining today are relevant for understanding and treating the modern circadian-rhythm-based disorders which are due to a misalignment between the internal circadian rhythms and the times for sleep, work, school and meals. PMID:25670162

Eastman, Charmane I; Suh, Christina; Tomaka, Victoria A; Crowley, Stephanie J

2015-01-01

200

Role for LSM genes in the regulation of circadian rhythms  

PubMed Central

Growing evidence suggests that core spliceosomal components differentially affect RNA processing of specific genes; however, whether changes in the levels or activities of these factors control specific signaling pathways is largely unknown. Here we show that some SM-like (LSM) genes, which encode core components of the spliceosomal U6 small nuclear ribonucleoprotein complex, regulate circadian rhythms in plants and mammals. We found that the circadian clock regulates the expression of LSM5 in Arabidopsis plants and several LSM genes in mouse suprachiasmatic nucleus. Further, mutations in LSM5 or LSM4 in Arabidopsis, or down-regulation of LSM3, LSM5, or LSM7 expression in human cells, lengthens the circadian period. Although we identified changes in the expression and alternative splicing of some core clock genes in Arabidopsis lsm5 mutants, the precise molecular mechanism causing period lengthening remains to be identified. Genome-wide expression analysis of either a weak lsm5 or a strong lsm4 mutant allele in Arabidopsis revealed larger effects on alternative splicing than on constitutive splicing. Remarkably, large splicing defects were not observed in most of the introns evaluated using RNA-seq in the strong lsm4 mutant allele used in this study. These findings support the idea that some LSM genes play both regulatory and constitutive roles in RNA processing, contributing to the fine-tuning of specific signaling pathways. PMID:25288739

Perez-Santángelo, Soledad; Mancini, Estefanía; Francey, Lauren J.; Schlaen, Ruben Gustavo; Chernomoretz, Ariel; Hogenesch, John B.; Yanovsky, Marcelo J.

2014-01-01

201

Circadian rhythms in Limulus photoreceptors. I. Intracellular studies  

PubMed Central

The sensitivity of the lateral eye of the horseshoe crab, Limulus polyphemus, is modulated by efferent optic nerve impulses transmitted from a circadian clock located in the brain (Barlow, R. B., Jr., S. J. Bolanowski, and M. L. Brachman. 1977. Science. 197:86-89). At night, the efferent impulses invade the retinular, eccentric, and pigment cells of every ommatidium, inducing multiple anatomical and physiological changes that combine to increase retinal sensitivity as much as 100,000 times. We developed techniques for recording transmembrane potentials from a single cell in situ for several days to determine what circadian changes in retinal sensitivity originate in the primary phototransducing cell, the retinular cell. We found that the direct efferent input to the photoreceptor cell decreases its noise and increases its response. Noise is decreased by reducing the rate of spontaneous bumps by up to 100%. The response is increased by elevating photon catch (photons absorbed per flash) as much as 30 times, and increasing gain (response per absorbed photon) as much as 40%. The cellular mechanism for reducing the rate of spontaneous quantum bumps is not known. The mechanism for increasing gain appears to be the modulation of ionic conductances in the photoreceptor cell membrane. The mechanism for increasing photon catch is multiple changes in the anatomy of retinal cells. We combine these cellular events in a proposed scheme for the circadian rhythm in the intensity coding of single photoreceptors. PMID:3559515

1987-01-01

202

Sleep and circadian rhythm disruption and recognition memory in schizophrenia.  

PubMed

Schizophrenia patients often show irregularities in sleep and circadian rhythms and deficits in recognition memory. Similar phenotypes are seen in schizophrenia-relevant genetic mouse models, such as synaptosomal associated protein of 25kDa (Snap-25) point mutant mice, vasoactive intestinal peptide receptor 2 (Vipr2) knockout mice, and neuregulin 1 (Nrg1)-deficient mice. Sleep and circadian abnormalities and impaired recognition memory may be causally related in both schizophrenia patients and schizophrenia-relevant mouse models, since sleep deprivation, abnormal photic input, and the manipulation of core clock genes (cryptochrome 1/2) can all disrupt object recognition memory in rodent models. The recognition deficits observed in patients and mouse models (both schizophrenia-related and -unrelated) are discussed here in terms of the dual-process theory of recognition, which postulates that there are two recognition mechanisms-recollection versus familiarity-that can be selectively impaired by brain lesions, neuropsychiatric conditions, and putatively, sleep and circadian rhythm disruption. However, based on this view, the findings from patient studies and studies using genetic mouse models (Nrg1 deficiency) seem to be inconsistent with each other. Schizophrenia patients are impaired at recollection (and to a lesser extent, familiarity judgments), but Nrg1-deficient mice are impaired at familiarity-based object recognition, raising concerns regarding the validity of using these genetically modified mice to model recognition phenotypes observed in patients. This issue can be resolved in future animal studies by examining performance in different variants of the spontaneous recognition task-the standard, perirhinal cortex-dependent, object recognition task versus the hippocampus-dependent object-place recognition task-in order to see which of the two recognition mechanisms is more disrupted. PMID:25707284

Tam, Shu K E; Pritchett, David; Brown, Laurence A; Foster, Russell G; Bannerman, David M; Peirson, Stuart N

2015-01-01

203

Circadian rhythms. Decoupling circadian clock protein turnover from circadian period determination.  

PubMed

The mechanistic basis of eukaryotic circadian oscillators in model systems as diverse as Neurospora, Drosophila, and mammalian cells is thought to be a transcription-and-translation-based negative feedback loop, wherein progressive and controlled phosphorylation of one or more negative elements ultimately elicits their own proteasome-mediated degradation, thereby releasing negative feedback and determining circadian period length. The Neurospora crassa circadian negative element FREQUENCY (FRQ) exemplifies such proteins; it is progressively phosphorylated at more than 100 sites, and strains bearing alleles of frq with anomalous phosphorylation display abnormal stability of FRQ that is well correlated with altered periods or apparent arrhythmicity. Unexpectedly, we unveiled normal circadian oscillations that reflect the allelic state of frq but that persist in the absence of typical degradation of FRQ. This manifest uncoupling of negative element turnover from circadian period length determination is not consistent with the consensus eukaryotic circadian model. PMID:25635104

Larrondo, Luis F; Olivares-Yañez, Consuelo; Baker, Christopher L; Loros, Jennifer J; Dunlap, Jay C

2015-01-30

204

Pigment dispersing hormone generates a circadian response to light in the crayfish, Procambarus clarkii.  

PubMed

Photoreceptor cells have been identified as important structures in the organization of the circadian system responsible for the generation and expression of the electroretinogram (ERG) circadian rhythm. They are the structures where the circadian periodicity is expressed (effectors) and which transform information from external light signals to be conducted to the pacemaker in order to induce adjustments of the rhythm (synchronizers). After isolation, eyestalks perfused in a pigment dispersing hormone (PDH) solution, show significant changes in receptor potential (RP) amplitude and duration. Exogenous PDH injected into intact crayfish induces a migration of retinal shielding pigments to a light-adapted state. A single dose of PDH produces advances or delays in the circadian rhythm of response to light of visual photoreceptors. All these effects depend on the circadian phase of PDH application. Consequently, the determination of the action of exogenous PDH on photoreceptor cells proved to be very helpful in understanding some mechanisms underlying the circadian organization of crayfish. PMID:17428715

Verde, M A; Barriga-Montoya, C; Fuentes-Pardo, B

2007-08-01

205

Circadian rhythms in fatty acid-induced depression of myocardial contractile function: Potential mediation by the circadian clock within the cardiomyocyte  

Technology Transfer Automated Retrieval System (TEKTRAN)

Circadian rhythms in susceptibility to cardiovascular (CV) pathologic events (e.g., arrhythmias, myocardial infarction) are well established. These phenomena have been explained largely by diurnal variations in neurohumoral influences, such as sympathetic activity. Circadian clocks are intracellular...

206

The Interplay of cis-Regulatory Elements Rules Circadian Rhythms in Mouse Liver  

PubMed Central

The mammalian circadian clock is driven by cell-autonomous transcriptional feedback loops that involve E-boxes, D-boxes, and ROR-elements. In peripheral organs, circadian rhythms are additionally affected by systemic factors. We show that intrinsic combinatorial gene regulation governs the liver clock. With a temporal resolution of 2 h, we measured the expression of 21 clock genes in mouse liver under constant darkness and equinoctial light-dark cycles. Based on these data and known transcription factor binding sites, we develop a six-variable gene regulatory network. The transcriptional feedback loops are represented by equations with time-delayed variables, which substantially simplifies modelling of intermediate protein dynamics. Our model accurately reproduces measured phases, amplitudes, and waveforms of clock genes. Analysis of the network reveals properties of the clock: overcritical delays generate oscillations; synergy of inhibition and activation enhances amplitudes; and combinatorial modulation of transcription controls the phases. The agreement of measurements and simulations suggests that the intrinsic gene regulatory network primarily determines the circadian clock in liver, whereas systemic cues such as light-dark cycles serve to fine-tune the rhythms. PMID:23144788

Koren?i?, Anja; Bordyugov, Grigory; Košir, Rok; Rozman, Damjana; Goli?nik, Marko; Herzel, Hanspeter

2012-01-01

207

The influence of circadian rhythms on pre-and post-prandial metabolism in the snake Lamprophis fuliginosus  

E-print Network

The influence of circadian rhythms on pre- and post-prandial metabolism in the snake Lamprophis energy cost of circadian rhythms. To estimate SMR, SDA, and identify metabolic variation associated with circadian cycles in nocturnally active African house snakes (Lamprophis fuliginosus), we measured oxygen

Hopkins, William A.

208

An approximation to the temporal order in endogenous circadian rhythms of genes implicated in human adipose tissue metabolism  

Technology Transfer Automated Retrieval System (TEKTRAN)

Although it is well established that human adipose tissue (AT) shows circadian rhythmicity, published studies have been discussed as if tissues or systems showed only one or few circadian rhythms at a time. To provide an overall view of the internal temporal order of circadian rhythms in human AT in...

209

Shape Invariant Modelling of Circadian Rhythms with Random E#ects and  

E-print Network

). For example, it is known that hormone cortisol levels peak in the morning and decrease to substantially lower (or sick) human subjects (or animals). The problems of interest are: (1) do circadian rhythms exist

Wang, Yuedong

210

Characterization of a circadian rhythm mutant identified in a genetic screen in Neurospora crassa  

E-print Network

the fungus is easy to manipulate, both genetically and biochemically, and the conidiation rhythm is easily monitored using specialized growth tubes called race tubes. One property of the circadian clock is that it can be reset by an environmental stimulus...

Keasler, Victor Vasco

2013-02-22

211

Treatment of a Circadian Rhythm Disturbance in a 2-Year-Old Blind Child.  

ERIC Educational Resources Information Center

The use of sleep scheduling and a daytime routine for the treatment of circadian rhythm disorder was found helpful in decreasing a blind 2-year old's nighttime wake periods and daytime sleepiness. (DB)

Mindell, J. A.; And Others

1996-01-01

212

Sleep and Circadian Rhythm Regulation in Early Parkinson Disease  

PubMed Central

IMPORTANCE Sleep disturbances are recognized as a common nonmotor complaint in Parkinson disease but their etiology is poorly understood. OBJECTIVE To define the sleep and circadian phenotype of patients with early-stage Parkinson disease. DESIGN, SETTING, AND PARTICIPANTS Initial assessment of sleep characteristics in a large population-representative incident Parkinson disease cohort (N=239) at the University of Cambridge, England, followed by further comprehensive case-control sleep assessments in a subgroup of these patients (n=30) and matched controls (n=15). MAIN OUTCOMES AND MEASURES Sleep diagnoses and sleep architecture based on polysomnography studies, actigraphy assessment, and 24-hour analyses of serum cortisol, melatonin, and peripheral clock gene expression (Bmal1, Per2, and Rev-Erb?). RESULTS Subjective sleep complaints were present in almost half of newly diagnosed patients and correlated significantly with poorer quality of life. Patients with Parkinson disease exhibited increased sleep latency (P = .04), reduced sleep efficiency (P = .008), and reduced rapid eye movement sleep (P = .02). In addition, there was a sustained elevation of serum cortisol levels, reduced circulating melatonin levels, and altered Bmal1 expression in patients with Parkinson disease compared with controls. CONCLUSIONS AND RELEVANCE Sleep dysfunction seen in early Parkinson disease may reflect a more fundamental pathology in the molecular clock underlying circadian rhythms. PMID:24687146

Nawarathna, Upekshani; Fisher, Kate; Shneerson, John M.; Reddy, Akhilesh B.; Barker, Roger A.

2014-01-01

213

Gravity and thermoregulation: metabolic changes and circadian rhythms  

NASA Technical Reports Server (NTRS)

Gravity appears to alter thermoregulation through changes in both the regulated level of body temperature and the rhythmic organization of temperature regulation. Gravity has been hypothesized to have an associated metabolic cost. Increased resting energy expenditure and dietary intake have been observed in animals during centrifuge experiments at hypergravity. Thus far, only animals have shown a corresponding reduction in metabolism in microgravity. Altered heat loss has been proposed as a response to altered gravitational environments, but remains documented only as changes in skin temperature. Changes in circadian timing, including the body temperature rhythm, have been shown in both hypergravity and microgravity, and probably contribute to alterations in sleep and performance. Changes in body temperature regulation may result from circadian disturbance, from the direct or indirect actions of gravity on the regulated temperature, or from changes in thermoregulatory effectors (heat production and heat loss) due to altered gravitational load and convective changes. To date, however, we have little data on the underlying thermoregulatory changes in altered gravity, and thus the precise mechanisms by which gravity alters temperature regulation remain largely unknown.

Robinson, E. L.; Fuller, C. A.

2000-01-01

214

Circadian Rhythms in Acute Intermittent Porphyria—a Pilot Study  

PubMed Central

Acute intermittent porphyria (AIP) is an inherited disorder of heme synthesis wherein a partial deficiency of porphobilinogen [PBG] deaminase [PBGD], with other factors may give rise to biochemical and clinical manifestations of disease. The biochemical hallmarks of active AIP are relative hepatic heme deficiency and uncontrolled up-regulation of hepatic 5-aminolevulinic acid [ALA] synthase-1 [ALAS1] with overproduction of ALA and PBG. The treatment of choice is intravenous heme, which restores the deficient regulatory heme pool of the liver and represses ALAS1. Recently, heme has been shown to influence circadian rhythms by controlling their negative feedback loops. We evaluated whether subjects with AIP exhibited an altered circadian profile. Over a 21 h period, we measured levels of serum cortisol, melatonin, ALA, PBG, and mRNA levels [in peripheral blood mononuclear cells] of selected clock-controlled genes and genes involved in heme synthesis in 10 Caucasian [European-American] women who were either post-menopausal or had been receiving female hormone therapy, 6 of whom have AIP and 4 do not and are considered controls. Four AIP subjects with biochemical activity exhibited higher levels of PBG and lower levels and dampened oscillation of serum cortisol, and a trend for lower levels of serum melatonin, than controls or AIP subjects without biochemical activity. Levels of clock-controlled gene mRNAs showed significant increases over baseline in all subjects at 5 am and 11 pm, whereas mRNA levels of ALAS1, ALAS2, and PBGD were increased only at 11 pm in subjects with active AIP. This pilot study provides evidence for disturbances of circadian markers in women with active AIP that may trigger or sustain some common clinical features of AIP. PMID:23650938

Larion, Sebastian; Caballes, F. Ryan; Hwang, Sun-Il; Lee, Jin-Gyun; Rossman, Whitney Ellefson; Parsons, Judy; Steuerwald, Nury; Li, Ting; Maddukuri, Vinaya; Groseclose, Gale; Finkielstein, Carla V.; Bonkovsky, Herbert L.

2013-01-01

215

Idiopathic chronic sleep onset insomnia in attention-deficit\\/hyperactivity disorder: a circadian rhythm sleep disorder  

Microsoft Academic Search

To investigate whether ADHD-related sleep-onset insomnia (SOI) is a circadian rhythm disorder, we compared actigraphic sleep estimates, the circadian rest-activity rhythm, and dim light melatonin onset (DLMO) in ADHD children having chronic idiopathic SOI with that in ADHD children without sleep problems. Participants were 87 psychotropic-medication-naive children, aged 6 to 12 yrs, with rigorously diagnosed ADHD and SOI (ADHD-SOI) and

Heijden van der K. B; M. G. Smits; Someren van E. J. W; W. B. Gunning

2005-01-01

216

The genetics of circadian rhythms in Neurospora crassa : do multiple oscillators exist?  

E-print Network

1997). At a broader level of similarities, all circadian rhythms are defined by the following four essential characteristics (Edmunds 1988): 1. Self-sustained oscillation under constant conditions 2. A period of approximately 24 hours 3.... "Circadian rhythms in a nutshell. " Physiol Genomi cs 3: 59-74, 2000. Edmunds, L. N. Jr. ( ellular andMolecular Bases of Biological Clocks. Models and Mechanisms for Ctrcadam Timekeeping. New York. Springer, 1988 Feldman, J. F and Hoyle, M N. "Isolation...

Kortum, Karen

2013-02-22

217

Non-Circadian Expression Masking Clock-Driven Weak Transcription Rhythms in U2OS Cells  

PubMed Central

U2OS cells harbor a circadian clock but express only a few rhythmic genes in constant conditions. We identified 3040 binding sites of the circadian regulators BMAL1, CLOCK and CRY1 in the U2OS genome. Most binding sites even in promoters do not correlate with detectable rhythmic transcript levels. Luciferase fusions reveal that the circadian clock supports robust but low amplitude transcription rhythms of representative promoters. However, rhythmic transcription of these potentially clock-controlled genes is masked by non-circadian transcription that overwrites the weaker contribution of the clock in constant conditions. Our data suggest that U2OS cells harbor an intrinsically rather weak circadian oscillator. The oscillator has the potential to regulate a large number of genes. The contribution of circadian versus non-circadian transcription is dependent on the metabolic state of the cell and may determine the apparent complexity of the circadian transcriptome. PMID:25007071

Hoffmann, Julia; Symul, Laura; Shostak, Anton; Fischer, Tamás; Naef, Felix; Brunner, Michael

2014-01-01

218

Circadian-Rhythm Sleep Disorders in Persons Who Are Totally Blind.  

ERIC Educational Resources Information Center

Discusses the diagnosis and management of "non-24-hour sleep-wake syndrome," a form of cyclic insomnia to which people who are totally blind are prone. Covered are incidence and clinical features, formal diagnostic criteria, the biological basis of circadian sleep disorders, circadian rhythms in blind people, pharmacological entrainment, and the…

Sack, R. L.; Blood, M. L.; Hughes, R. J.; Lewy, A. J.

1998-01-01

219

Modeling oxaliplatin drug delivery to circadian rhythms in drug metabolism and host tolerance  

E-print Network

Modeling oxaliplatin drug delivery to circadian rhythms in drug metabolism and host tolerance Jean 2006 Available online 28 June 2007 Abstract To make possible the design of optimal (circadian and other period) time-scheduled regimens for cytotoxic drug delivery by intravenous infusion, a pharmacokinetic

Clairambault, Jean

220

Inversion of the circadian rhythm of melatonin in the Smith-Magenis syndrome  

Microsoft Academic Search

Objective: The objective was to determine the circadian rhythm of mela- tonin in the Smith-Magenis syndrome (SMS), which causes behavioral problems and sleep disturbance. Study design: Questionnaires, sleep consultations, and sleep diaries were obtained in 20 children with SMS (9 girls, 11 boys aged 4 to 17 years). Actigraphy, electroencephalography, and the circadian variations of plasma melatonin, cortisol, and growth

Marie-Christine de Blois; Bruno Claustrat; Serge Romana; Urs Albrecht; Bruno Delobel; Géraldine Viot; Stanislas Lyonnet; Michel Vekemans; Arnold Munnich

221

Inversion of the circadian rhythm of melatonin in the Smith-Magenis syndrome  

Microsoft Academic Search

Objective: The objective was to determine the circadian rhythm of melatonin in the Smith-Magenis syndrome (SMS), which causes behavioral problems and sleep disturbance. Study design: Questionnaires, sleep consultations, and sleep diaries were obtained in 20 children with SMS (9 girls, 11 boys aged 4 to 17 years). Actigraphy, electroencephalography, and the circadian variations of plasma melatonin, cortisol, and growth hormone

Hélène De Leersnyder; Marie-Christine de Blois; Bruno Claustrat; Serge Romana; Urs Albrecht; Jürgen-Christoph von Kleist-Retzow; Bruno Delobel; Géraldine Viot; Stanislas Lyonnet; Michel Vekemans; Arnold Munnich

2001-01-01

222

Circadian and ultradian rhythms of drinking behavior of albino rats maintained in constant darkness.  

PubMed

The objective of the present study was to investigate the circadian and the ultradian rhythms of drinking behavior in Wistar rats maintained under conditions of constant darkness. Six mature male rats (weighing 270-350 g) were exposed to light-dark 12:12-h cycles (LD 12:12, light on at 12:00 h) for 35 days and then switched to constant darkness (DD) conditions for at least 2 weeks. Drinking behavior was monitored continuously with a standard drinkometer circuit and the data was stored in 5-min bins. A modification of Enright's periodogram technique was used to evaluate the free-running drinking behavior circadian rhythm. Ultradian rhythms in drinking behavior were estimated by the Fast Fourier Transform (FFT) technique. Two of the animals (rats 4 and 6) showed no statistically significant circadian or ultradian rhythms and the other four showed free-running drinking circadian rhythm behavior shorter than 24 h (ranging from 23.333 to 23.967 h). Ultradian rhythms of drinking behavior of 12- and 8-h periods were detected in 4 (rats 1, 2, 3 and 5) and 2 (rats 1 and 5) animals, respectively. The relation of the compound structure of the circadian and ultradian rhythms is discussed demonstrating that drinking behavior is a good marker for studies of physiology of temporal organization. PMID:9181111

Araujo, J F; Marques, N

1996-10-01

223

Fatigue and Circadian Activity Rhythms in Breast Cancer Patients Before and After Chemotherapy: A Controlled Study  

PubMed Central

Background Breast cancer (BC) patients often experience cancer-related fatigue (CRF) before, during, and after their chemotherapy. Circadian rhythms are 24-hour cycles of behavior and physiology that are generated by internal pacemakers and entrained by zeitgebers (e.g., light). A few studies have suggested a relationship between fatigue and circadian rhythms in some clinical populations. Methods One hundred and forty-eight women diagnosed with stage I-III breast cancer and scheduled to receive at least four cycles of adjuvant or neoadjuvant chemotherapy, and 61 controls (cancer-free healthy women) participated in this study. Data were collected before (Baseline) and after four cycles of chemotherapy (Cycle-4). Fatigue was assessed with the Short Form of Multidimensional Fatigue Symptom Inventory (MFSI-SF); circadian activity rhythm (CAR) was recorded with wrist actigraphy (six parameters included: amplitude, acrophase, mesor, up-mesor, down-mesor and F-statistic). A mixed model analysis was used to examine changes in fatigue and CAR parameters compared to controls, and to examine the longitudinal relationship between fatigue and CAR parameters in BC patients. Results More severe CRF (total and subscale scores) and disrupted CAR (amplitude, mesor and F-statistic) were observed in BC patients compared to controls at both Baseline and Cycle-4 (all p's<0.05); BC patients also experienced more fatigue and decreased amplitude and mesor, as well as delayed up-mesor time at Cycle-4 compared to Baseline (all p's<0.05). The increased total MFSI-SF scores were significantly associated with decreased amplitude, mesor and F-statistic (all p's<0.006). Conclusion CRF exists and CAR is disrupted even before the start of chemotherapy. The significant relationship between CRF and CAR indicate possible underlying connections. Re-entraining the disturbed CAR using effective interventions such as bright light therapy might also improve CRF. PMID:23412418

Liu, Lianqi; Rissling, Michelle; Neikrug, Ariel; Fiorentino, Lavinia; Natarajan, Loki; Faierman, Michelle; Sadler, Georgia Robins; Dimsdale, Joel E.; Mills, Paul J.; Parker, Barbara A.; Ancoli-Israel, Sonia

2013-01-01

224

Circadian rhythms in the pineal organ persist in zebrafish larvae that lack ventral brain  

PubMed Central

Background The mammalian suprachiasmatic nucleus (SCN), located in the ventral hypothalamus, is a major regulator of circadian rhythms in mammals and birds. However, the role of the SCN in lower vertebrates remains poorly understood. Zebrafish cyclops (cyc) mutants lack ventral brain, including the region that gives rise to the SCN. We have used cyc embryos to define the function of the zebrafish SCN in regulating circadian rhythms in the developing pineal organ. The pineal organ is the major source of the circadian hormone melatonin, which regulates rhythms such as daily rest/activity cycles. Mammalian pineal rhythms are controlled almost exclusively by the SCN. In zebrafish and many other lower vertebrates, the pineal has an endogenous clock that is responsible in part for cyclic melatonin biosynthesis and gene expression. Results We find that pineal rhythms are present in cyc mutants despite the absence of an SCN. The arginine vasopressin-like protein (Avpl, formerly called Vasotocin) is a peptide hormone expressed in and around the SCN. We find avpl mRNA is absent in cyc mutants, supporting previous work suggesting the SCN is missing. In contrast, expression of the putative circadian clock genes, cryptochrome 1b (cry1b) and cryptochrome 3 (cry3), in the brain of the developing fish is unaltered. Expression of two pineal rhythmic genes, exo-rhodopsin (exorh) and serotonin-N-acetyltransferase (aanat2), involved in photoreception and melatonin synthesis, respectively, is also similar between cyc embryos and their wildtype (WT) siblings. The timing of the peaks and troughs of expression are the same, although the amplitude of expression is slightly decreased in the mutants. Cyclic gene expression persists for two days in cyc embryos transferred to constant light or constant dark, suggesting a circadian clock is driving the rhythms. However, the amplitude of rhythms in cyc mutants kept in constant conditions decreased more quickly than in their WT siblings. Conclusion Our data suggests that circadian rhythms can be initiated and maintained in the absence of SCN and other tissues in the ventral brain. However, the SCN may have a role in regulating the amplitude of rhythms when environmental cues are absent. This provides some of the first evidence that the SCN of teleosts is not essential for establishing circadian rhythms during development. Several SCN-independent circadian rhythms have also been found in mammalian species. Thus, zebrafish may serve as a model system for understanding how vertebrate embryos coordinate rhythms that are controlled by different circadian clocks. PMID:21232144

2011-01-01

225

Circadian Intraocular Pressure Rhythms in Athletic Horses under Different Lighting Regime  

Microsoft Academic Search

The present study was undertaken to investigate the existence of intraocular pressure (IOP) rhythms in athletic thoroughbred horses maintained under a 24 h cycle of light and darkness (LD) or under constant light (LL) or constant dark (DD) conditions. We identified an IOP circadian rhythm that is entrained to the 24 h LD cycle. IOP was low during the dark

Cristiano Bertolucci; Elisabetta Giudice; Francesco Fazio; Giuseppe Piccione

2009-01-01

226

Circadian rhythms and mood regulation: Insights from pre-clinical models  

Microsoft Academic Search

Affective disorders such as major depression, bipolar disorder, and seasonal affective disorder are associated with major disruptions in circadian rhythms. Indeed, altered sleep\\/wake cycles are a critical feature for diagnosis in the DSM IV and several of the therapies used to treat these disorders have profound effects on rhythm length and stabilization in human populations. Furthermore, multiple human genetic studies

Colleen A. McClung

2011-01-01

227

Bright Light Therapy Protects Women from Circadian Rhythm Desynchronization during Chemotherapy for Breast-Cancer  

Microsoft Academic Search

Purpose: Circadian rhythms (CR) are commonly disrupted in women undergoing chemotherapy for breast cancer (BC). Bright light improves and strengthens CR in other populations. This randomized controlled study examined the effect of morning administration of bright light therapy on CR in women undergoing chemotherapy for BC. We hypothesized that women receiving bright light therapy would exhibit more robust rhythms than

Ariel B. Neikrug; Michelle Rissling; Vera Trofimenko; Lianqi Liu; Loki Natarajan; Susan Lawton; Barbara A. Parker; Sonia Ancoli-Israel

2012-01-01

228

Bright Light Therapy Protects Women from Circadian Rhythm Desynchronization During Chemotherapy for Breast Cancer  

Microsoft Academic Search

Circadian rhythms (CRs) are commonly disrupted in women undergoing chemotherapy for breast cancer (BC). Bright light improves and strengthens CRs in other populations. This randomized controlled study examined the effect of morning administration of bright light therapy on CRs in women undergoing chemotherapy for BC. It was hypothesized that women receiving bright light therapy would exhibit more robust rhythms than

Ariel B. Neikrug; Michelle Rissling; Vera Trofimenko; Lianqi Liu; Loki Natarajan; Susan Lawton; Barbara A. Parker; Sonia Ancoli-Israel

2012-01-01

229

Photocontrol of Dark Circadian Rhythms in Stomata of Phaseolus vulgaris L  

PubMed Central

Stomatal diffusion resistance in primary leaves of Phaseolus vulgaris L. which had been grown in light:dark cycles followed a marked circadian rhythm when the plants were transferred to continuous darkness. Reentrainment of the rhythm required more than one inductive change in photoperiod. The phasing of the rhythm of dark stomatal opening was contolled primarily by the light-on (dawn) signal, whereas the rhythm of dark closure was related to the light-off (dusk) signal. The evidence points to a dual control of the circadian clock in which a product of photosynthesis plays a major role. No evidence for phytochrome involvement in the phasing of the rhythm was found. An influence of phytochrome on the amplitude of the stomatal rhythm was observed in which removal of phytochrome-far-red absorbing form caused rapid damping. PMID:16665006

Holmes, M. Geoffrey; Klein, William H.

1986-01-01

230

Entrainment of the circadian activity rhythm of a lizard to melatonin injections.  

PubMed

The circadian activity rhythms of lizards (Sceloporus occidentalis) can be entrained (synchronized) to a period of 24 hr by melatonin injections given every other day at the same time of day, but not by saline injections. The activity onsets of the entrained lizards exhibited two preferred phase-relationships (approximately 165 degrees and approximately 30 degrees) with the time of melatonin injections with the 30 degree phase only rarely observed. These results suggest that endogenous rhythms of melatonin secretion (i.e., from the pineal organ) may be involved in synchronizing circadian oscillations within the lizard's multioscillator circadian system. PMID:4070395

Underwood, H; Harless, M

1985-08-01

231

Individual variation in circadian rhythms of sleep, EEG, temperature, and activity among monkeys - Implications for regulatory mechanisms.  

NASA Technical Reports Server (NTRS)

Investigation of circadian rhythms in a number of variables related to sleep, EEG, temperature, and motor activity in rhesus monkeys on an LD 12:12 schedule. Circadian rhythms were found to appear in each of 15 variables investigated. Statistical procedures assessed the variables for evidence of common regulation in these aspects of their circadian rhythms: acrophase (timing), amplitude (extent of change), and level (24-hr mean value). Patterns appearing in the data suggested that the circadian rhythms of certain variables are regulated in common. The circadian modulation of activity in the beta and sigma frequency bands of the EEG was correlated with statistical significance in acrophase, level, and amplitude. The delta frequency band appeared to be under circadian rhythm regulation distinct from that of the other bands. The circadian rhythm of REM stage sleep was like that of beta activity in level and amplitude. The data indicate that REM stage may share some common regulation of circadian timing with both stage 3-4 sleep and with temperature. Generally, however, the circadian rhythm of temperature appeared to bear little relation to the circadian rhythms of motor activity, EEG, or sleep.

Crowley, T. J.; Halberg, F.; Kripke, D. F.; Pegram, G. V.

1971-01-01

232

A peripheral pacemaker drives the circadian rhythm of synaptic boutons in Drosophila independently of synaptic activity  

Microsoft Academic Search

Circadian rhythms in the morphology of neurons have been demonstrated in the fly Drosophila melanogaster. One such rhythm is characterized by changes in the size of synaptic boutons of an identified flight motor neuron, with larger\\u000a boutons during the day compared with those at night. A more detailed temporal resolution of this rhythm shows here that boutons\\u000a grow at a

Kerstin I. Mehnert; Rafael Cantera

2008-01-01

233

Effect of Spaceflight on the Circadian Rhythm, Lifespan and Gene Expression of Drosophila melanogaster  

PubMed Central

Space travelers are reported to experience circadian rhythm disruption during spaceflight. However, how the space environment affects circadian rhythm is yet to be determined. The major focus of this study was to investigate the effect of spaceflight on the Drosophila circadian clock at both the behavioral and molecular level. We used China’s Shenzhou-9 spaceship to carry Drosophila. After 13 days of spaceflight, behavior tests showed that the flies maintained normal locomotor activity rhythm and sleep pattern. The expression level and rhythm of major clock genes were also unaffected. However, expression profiling showed differentially regulated output genes of the circadian clock system between space flown and control flies, suggesting that spaceflight affected the circadian output pathway. We also investigated other physiological effects of spaceflight such as lipid metabolism and lifespan, and searched genes significantly affected by spaceflight using microarray analysis. These results provide new information on the effects of spaceflight on circadian rhythm, lipid metabolism and lifespan. Furthermore, we showed that studying the effect of spaceflight on gene expression using samples collected at different Zeitgeber time could obtain different results, suggesting the importance of appropriate sampling procedures in studies on the effects of spaceflight. PMID:25798821

Xu, Kanyan

2015-01-01

234

The circadian rhythm in adult attention-deficit/hyperactivity disorder: current state of affairs.  

PubMed

Adults with ADHD often have sleep problems that are caused by a delay of their internal circadian rhythm system. Such individuals are often typified as 'evening' or 'night' persons. This review focuses on the link between ADHD symptoms and the evening typology through multiple pathways. Etiology of the internal circadian rhythm system, the genetic basis for evening typology, overlap between ADHD symptoms and evening preference and risk factors for various chronic health conditions, including metabolic syndrome and cancer, are discussed. The treatment perspectives to reset the delayed rhythm in adults with ADHD involve psychoeducation on sleep hygiene, melatonin in the afternoon or evening and bright light therapy in the morning. PMID:24117273

Kooij, J J Sandra; Bijlenga, Denise

2013-10-01

235

Longitudinal Stability and Developmental Properties of Salivary Cortisol Levels and Circadian Rhythms from Childhood to Adolescence  

PubMed Central

This study aimed to (1) identify a stable, trait-like component to cortisol and its circadian rhythm, and (2) investigate individual differences in developmental trajectories of HPA-axis maturation. Multiple salivary cortisol samples were collected longitudinally across four assessments from age 9 (3rd grade) through age 15 (9th grade) in a community sample of children (N=357). Sophisticated statistical models examined cortisol levels and its rhythm over time; effects of age, puberty and gender were primarily considered. In addition to situation-specific and stable short-term or epoch-specific cortisol components, there is a stable, trait-like component of cortisol levels and circadian rhythm across multiple years covering the transition from childhood into adolescence. Youth had higher cortisol and flatter circadian rhythms as they got older and more physically developed. Girls had higher cortisol, stronger circadian rhythms, and greater developmental influences across adolescence. Distinguishing a stable, trait-like component of cortisol level and its circadian rhythm provides the empirical foundation for investigating putative mechanisms underlying individual differences in HPA functioning. The findings also provide important descriptive information about maturational processes influencing HPA-axis development. PMID:21953537

Shirtcliff, Elizabeth A.; Allison, Amber L.; Armstrong, Jeffrey M.; Slattery, Marcia J.; Kalin, Ned H.; Essex, Marilyn J.

2011-01-01

236

Estrogen receptor 1 modulates circadian rhythms in adult female mice.  

PubMed

Estradiol influences the level and distribution of daily activity, the duration of the free-running period, and the behavioral phase response to light pulses. However, the mechanisms by which estradiol regulates daily and circadian rhythms are not fully understood. We tested the hypothesis that estrogens modulate daily activity patterns via both classical and "non-classical" actions at the estrogen receptor subtype 1 (ESR1). We used female transgenic mice with mutations in their estrogen response pathways; ESR1 knock-out (ERKO) mice and "non-classical" estrogen receptor knock-in (NERKI) mice. NERKI mice have an ESR1 receptor with a mutation in the estrogen-response-element binding domain, allowing only actions via "non-classical" genomic and second messenger pathways. Ovariectomized female NERKI, ERKO, and wildtype (WT) mice were given a subcutaneous capsule with low- or high-dose estradiol and compared with counterparts with no hormone replacement. We measured wheel-running activity in a light:dark cycle and constant darkness, and the behavioral phase response to light pulses given at different points during the subjective day and night. Estradiol increased average daily wheel-running, consolidated activity to the dark phase, and shortened the endogenous period in WT, but not NERKI and ERKO mice. The timing of activity onset during entrainment was advanced in all estradiol-treated animals regardless of genotype suggesting an ESR1-independent mechanism. We propose that estradiol modifies period, activity level, and distribution of activity via classical actions of ESR1 whereas an ESR1 independent mechanism regulates the phase of rhythms. PMID:24527952

Blattner, Margaret S; Mahoney, Megan M

2014-06-01

237

Comparison of hormone and electrolyte circadian rhythms in male and female humans  

NASA Technical Reports Server (NTRS)

Circadian rhythm characteristics in healthy male and female humans were studied at 4-hour intervals for urine volume, cortisol, 5-hydroxyindoleacetic acid (5-HIAA), Na, K, Na/K ratios in the urine, as well as plasma cortisol. While plasma and urinary cortisol rhythms were very similar in both sexes, the described rhythms in urine volume, electrolyte, and 5-HIAA excretion differ for the two sexes. The results suggest that sex differences exist in the circadian patterns of important hormone and metabolic functions and that the internal synchrony of circadian rhythms differs for the two sexes. The results seem to indicate that the rhythmical secretion of cortisol does not account for the pattern of Na and K excretion.

Vernikos-Danellis, J.; Winget, C. M.; Goodwin, A. E.; Reilly, T.

1977-01-01

238

Skin surface temperature rhythms as potential circadian biomarkers for personalized chronotherapeutics in cancer patients  

PubMed Central

Chronotherapeutics involve the administration of treatments according to circadian rhythms. Circadian timing of anti-cancer medications has been shown to improve treatment tolerability up to fivefold and double efficacy in experimental and clinical studies. However, the physiological and the molecular components of the circadian timing system (CTS), as well as gender, critically affect the success of a standardized chronotherapeutic schedule. In addition, a wrongly timed therapy or an excessive drug dose disrupts the CTS. Therefore, a non-invasive approach to accurately detect and monitor circadian rhythms is needed for a dynamic assessment of the CTS in order to personalize chronomodulated drug delivery schedule in cancer patients. Since core body temperature is a robust circadian biomarker, we recorded temperature at multiple locations on the skin of the upper chest and back of controls and cancer patients continuously. Variability in the circadian phase existed among patch locations in individual subjects over the course of 2–6 days, demonstrating the need to monitor multiple skin temperature locations to determine the precise circadian phase. Additionally, we observed that locations identified by infrared imaging as relatively cool had the largest 24 h temperature variations. Disruptions in skin temperature rhythms during treatment were found, pointing to the need to continually assess circadian timing and personalize chronotherapeutic schedules. PMID:21544221

Scully, Christopher G.; Karaboué, Abdoulaye; Liu, Wei-Min; Meyer, Joseph; Innominato, Pasquale F.; Chon, Ki H.; Gorbach, Alexander M.; Lévi, Francis

2011-01-01

239

A Long Noncoding RNA Perturbs the Circadian Rhythm of Hepatoma Cells to Facilitate Hepatocarcinogenesis12  

PubMed Central

Clock circadian regulator (CLOCK)/brain and muscle arnt-like protein-1 (BMAL1) complex governs the regulation of circadian rhythm through triggering periodic alterations of gene expression. However, the underlying mechanism of circadian clock disruption in hepatocellular carcinoma (HCC) remains unclear. Here, we report that a long noncoding RNA (lncRNA), highly upregulated in liver cancer (HULC), contributes to the perturbations in circadian rhythm of hepatoma cells. Our observations showed that HULC was able to heighten the expression levels of CLOCK and its downstream circadian oscillators, such as period circadian clock 1 and cryptochrome circadian clock 1, in hepatoma cells. Strikingly, HULC altered the expression pattern and prolonged the periodic expression of CLOCK in hepatoma cells. Mechanistically, the complementary base pairing between HULC and the 5' untranslated region of CLOCK mRNA underlay the HULC-modulated expression of CLOCK, and the mutants in the complementary region failed to achieve the event. Moreover, immunohistochemistry staining and quantitative real-time polymerase chain reaction validated that the levels of CLOCK were elevated in HCC tissues, and the expression levels of HULC were positively associated with those of CLOCK in clinical HCC samples. In functional experiments, our data exhibited that CLOCK was implicated in the HULC-accelerated proliferation of hepatoma cells in vitro and in vivo. Taken together, our data show that an lncRNA, HULC, is responsible for the perturbations in circadian rhythm through upregulating circadian oscillator CLOCK in hepatoma cells, resulting in the promotion of hepatocarcinogenesis. Thus, our finding provides new insights into the mechanism by which lncRNA accelerates hepatocarcinogenesis through disturbing circadian rhythm of HCC. PMID:25622901

Cui, Ming; Zheng, Minying; Sun, Baodi; Wang, Yue; Ye, Lihong; Zhang, Xiaodong

2015-01-01

240

Pinealectomy does not affect the entrainment to light nor the generation of the circadian demand-feeding rhythms of rainbow trout  

Microsoft Academic Search

The pineal organ and its secretory product melatonin are regarded as synchronizers of daily rhythms to the external light\\/dark (LD) cycle. In fish, the pineal organ acts as a direct photoreceptor, transducing light information into neural and humoral (melatonin) signals. In the present study, we investigate a possible role for the pineal organ and melatonin in the regulation of feeding

Masayuki Iigo; Juan Antonio Madrid; Mitsuo Tabata

2000-01-01

241

Circadian rhythm of aldosterone in dairy cattle during the summer  

NASA Astrophysics Data System (ADS)

Twelve Holstein heifers, pregnant from 120 150 days were used to study the circadian rhythm of aldosterone, cortisol, progesterone, sodium and potassium in dairy cattle during the summer in Louisiana. Cortisol was not significantly influenced by time (time 1 = 06.00 h). Aldosterone, sodium, potassium and progesterone changed significantly (P<.01) with time. Aldosterone peaked (116.5±17.2 pg/ml) at 08.00 h and then generally declined to 16.00 h (26.7±2.0 pg/ml). Sodium generally increased from 06.00 h (320.1±7.3 mg%) to 18.00 h (377.9±6.1 mg%), and then declined. Potassium generally increased from 06.00 h (20.9±0.5 mg%) to 22.00 h (23.0±0.3 mg%). Progesterone generally increased from 07.00 h (2.8±0.4 mg/ml) to 24.00 h (7.5±1.4 mg/ml). Aldosterone was significantly related to temperature associated with the time of the day samples were taken (r = 0.66, P<.02).

Aranas, T. J.; Roussel, J. D.; Seybt, S. H.

1987-09-01

242

A simple model of circadian rhythms based on dimerization and proteolysis of PER and TIM  

PubMed Central

Many organisms display rhythms of physiology and behavior that are entrained to the 24-h cycle of light and darkness prevailing on Earth. Under constant conditions of illumination and temperature, these internal biological rhythms persist with a period close to 1 day ("circadian"), but it is usually not exactly 24 h. Recent discoveries have uncovered stunning similarities among the molecular circuitries of circadian clocks in mice, fruit flies, and bread molds. A consensus picture is coming into focus around two proteins (called PER and TIM in fruit flies), which dimerize and then inhibit transcription of their own genes. Although this picture seems to confirm a venerable model of circadian rhythms based on time-delayed negative feedback, we suggest that just as crucial to the circadian oscillator is a positive feedback loop based on stabilization of PER upon dimerization. These ideas can be expressed in simple mathematical form (phase plane portraits), and the model accounts naturally for several hallmarks of circadian rhythms, including temperature compensation and the per(L) mutant phenotype. In addition, the model suggests how an endogenous circadian oscillator could have evolved from a more primitive, light-activated switch. PMID:20540926

Tyson, JJ; Hong, CI; Thron, CD; Novak, B

1999-01-01

243

Robust circadian rhythms of gene expression in Brassica rapa tissue culture.  

PubMed

Circadian clocks provide temporal coordination by synchronizing internal biological processes with daily environmental cycles. To date, study of the plant circadian clock has emphasized Arabidopsis (Arabidopsis thaliana) as a model, but it is important to determine the extent to which this model applies in other species. Accordingly, we have investigated circadian clock function in Brassica rapa. In Arabidopsis, analysis of gene expression in transgenic plants in which luciferase activity is expressed from clock-regulated promoters has proven a useful tool, although technical challenges associated with the regeneration of transgenic plants has hindered the implementation of this powerful tool in B. rapa. The circadian clock is cell autonomous, and rhythmicity has been shown to persist in tissue culture from a number of species. We have established a transgenic B. rapa tissue culture system to allow the facile measurement and manipulation of clock function. We demonstrate circadian rhythms in the expression of several promoter:LUC reporters in explant-induced tissue culture of B. rapa. These rhythms are temperature compensated and are reset by light and temperature pulses. We observe a strong positive correlation in period length between the tissue culture rhythm in gene expression and the seedling rhythm in cotyledon movement, indicating that the circadian clock in B. rapa tissue culture provides a good model for the clock in planta. PMID:20406912

Xu, Xiaodong; Xie, Qiguang; McClung, C Robertson

2010-06-01

244

Replication of cortisol circadian rhythm: new advances in hydrocortisone replacement therapy  

PubMed Central

Cortisol has one of the most distinct and fascinating circadian rhythms in human physiology. This is regulated by the central clock located in the suprachiasmatic nucleus of the hypothalamus. It has been suggested that cortisol acts as a secondary messenger between central and peripheral clocks, hence its importance in the synchronization of body circadian rhythms. Conventional immediate-release hydrocortisone, either at twice- or thrice-daily doses, is not capable of replicating physiological cortisol circadian rhythm and patients with adrenal insufficiency or congenital adrenal hyperplasia still suffer from a poor quality of life and increased mortality. Novel treatments for replacement therapy are therefore essential. Proof-of-concept studies using hydrocortisone infusions suggest that the circadian delivery of hydrocortisone may improve biochemical control and life quality in patients lacking cortisol with an impaired cortisol rhythm. Recently oral formulations of modified-release hydrocortisone are being developed and it has been shown that it is possible to replicate cortisol circadian rhythm and also achieve better control of morning androgen levels. These new drug therapies are promising and potentially offer a more effective treatment with less adverse effects. Definite improvements clearly need to be established in future clinical trials. PMID:23148157

Chan, Sharon; Debono, Miguel

2010-01-01

245

Wheel-running activity modulates circadian organization and the daily rhythm of eating behavior  

PubMed Central

Consumption of high-fat diet acutely alters the daily rhythm of eating behavior and circadian organization (the phase relationship between oscillators in central and peripheral tissues) in mice. Voluntary wheel-running activity counteracts the obesogenic effects of high-fat diet and also modulates circadian rhythms in mice. In this study, we sought to determine whether voluntary wheel-running activity could prevent the proximate effects of high-fat diet consumption on circadian organization and behavioral rhythms in mice. Mice were housed with locked or freely rotating running wheels and fed chow or high-fat diet for 1 week and rhythms of locomotor activity, eating behavior, and molecular timekeeping (PERIOD2::LUCIFERASE luminescence rhythms) in ex vivo tissues were measured. Wheel-running activity delayed the phase of the liver rhythm by 4 h in both chow- and high-fat diet-fed mice. The delayed liver phase was specific to wheel-running activity since an enriched environment without the running wheel did not alter the phase of the liver rhythm. In addition, wheel-running activity modulated the effect of high-fat diet consumption on the daily rhythm of eating behavior. While high-fat diet consumption caused eating events to be more evenly dispersed across the 24 h-day in both locked-wheel and wheel-running mice, the effect of high-fat diet was much less pronounced in wheel-running mice. Together these data demonstrate that wheel-running activity is a salient factor that modulates liver phase and eating behavior rhythms in both chow- and high-fat-diet fed mice. Wheel-running activity in mice is both a source of exercise and a self-motivating, rewarding behavior. Understanding the putative reward-related mechanisms whereby wheel-running activity alters circadian rhythms could have implications for human obesity since palatable food and exercise may modulate similar reward circuits. PMID:24624109

Pendergast, Julie S.; Branecky, Katrina L.; Huang, Roya; Niswender, Kevin D.; Yamazaki, Shin

2014-01-01

246

Non-peptide oxytocin receptor ligands and hamster circadian wheel running rhythms.  

PubMed

The synchronization of circadian rhythms in sleep, endocrine and metabolic functions with the environmental light cycle is essential for health, and dysfunction of this synchrony is thought to play a part in the development of many neurological disorders. There is a demonstrable need to develop new therapeutics for the treatment of neurological disorders such as depression and schizophrenia, and oxytocin is currently being investigated for this purpose. There are no published reports describing activity of oxytocin receptor ligands on mammalian circadian rhythms and that, then, is the purpose of this study. Non-peptide oxytocin receptor ligands that cross the blood brain barrier were systemically injected in hamsters to determine their ability to modulate light-induced phase advances and delays of circadian wheel running rhythms. The oxytocin receptor agonist WAY267464 (10 mg/kg) inhibited light induced phase advances of wheel running rhythms by 55%, but had no effect on light-induced phase delays. In contrast, the oxytocin receptor antagonist WAY162720 (10 mg/kg) inhibited light-induced phase delays by nearly 75%, but had no effect on light-induced phase advances. Additionally, WAY162720 was able to antagonize the inhibitory effects of WAY267464 on light-induced phase advances. These results are consistent for a role of oxytocin in the phase-delaying effects of light on circadian activity rhythms early in the night. Therefore, oxytocin may prove to be useful in developing therapeutics for the treatment of mood disorders with a concomitant dysfunction in circadian rhythms. Investigators should also be cognizant that oxytocin ligands may negatively affect circadian rhythms during clinical trials for other conditions. PMID:25148710

Gannon, Robert L

2014-10-17

247

Melanopsin resets circadian rhythms in cells by inducing clock gene Period1  

NASA Astrophysics Data System (ADS)

The biochemical, physiological and behavioral processes are under the control of internal clocks with the period of approximately 24 hr, circadian rhythms. The expression of clock gene Period1 (Per1) oscillates autonomously in cells and is induced immediately after a light pulse. Per1 is an indispensable member of the central clock system to maintain the autonomous oscillator and synchronize environmental light cycle. Per1 expression could be detected by Per1?luc and Per1?GFP plasmid DNA in which firefly luciferase and Green Fluorescence Protein were rhythmically expressed under the control of the mouse Per1 promoter in order to monitor mammalian circadian rhythms. Membrane protein, MELANOPSIN is activated by blue light in the morning on the retina and lead to signals transduction to induce Per1 expression and to reset the phase of circadian rhythms. In this report Per1 induction was measured by reporter signal assay in Per1?luc and Per1?GFP fibroblast cell at the input process of circadian rhythms. To the result all process to reset the rhythms by Melanopsin is completed in single cell like in the retina projected to the central clock in the brain. Moreover, the phase of circadian rhythm in Per1?luc cells is synchronized by photo-activated Melanopsin, because the definite peak of luciferase activity in one dish was found one day after light illumination. That is an available means that physiological circadian rhythms could be real-time monitor as calculable reporter (bioluminescent and fluorescent) chronological signal in both single and groups of cells.

Yamashita, Shuhei; Uehara, Tomoe; Matsuo, Minako; Kikuchi, Yo; Numano, Rika

2014-02-01

248

Genetic basis of incidence and period length of circadian rhythm for locomotor activity in populations of a seed beetle  

Microsoft Academic Search

Circadian rhythms are ubiquitous in a wide variety of organisms, although their genetic variation has been analyzed in only a few species. We found genetic differences in the circadian rhythm of adult locomotor activity among strains of the adzuki bean beetle, Callosobruchus chinensis, which differed in origin and have been maintained in isolation. All beetles in some strains clearly had

T Harano; T Miyatake

2010-01-01

249

Resetting of circadian melatonin and cortisol rhythms in humans by ordinary room light  

NASA Technical Reports Server (NTRS)

The present study was designed to investigate whether a weak photic stimulus can reset the endogenous circadian rhythms of plasma melatonin and plasma cortisol in human subjects. A stimulus consisting of three cycles of 5 h exposures to ordinary room light (approximately 180 lux), centered 1.5 h after the endogenous temperature nadir, significantly phase-advanced the plasma melatonin rhythm in eight healthy young men compared with the phase delays observed in eight control subjects who underwent the same protocol but were exposed to darkness (p < or = 0.003). After light-induced phase advances, the circadian rhythms of plasma melatonin and plasma cortisol maintained stable temporal relationships with the endogenous core body temperature cycle, consistent with the conclusion that exposure to ordinary indoor room light had shifted a master circadian pacemaker.

Boivin, D. B.; Czeisler, C. A.

1998-01-01

250

The possible long-term effects of early-life circadian rhythm disturbance on social behavior.  

PubMed

Sleep loss impairs brain function. As late sleep onset can reduce sleep, this sleep/circadian rhythm disturbance may cause brain impairment. Specific data on the long-term effects of sleep/circadian rhythm disturbance on subsequent brain function are lacking. Japan, a sleep-deprived society from infancy to adulthood, provides an ideal platform to investigate the association of these disturbances in early life with subsequent functioning. In this article, several current problematic behaviors among youth in Japan (dropping out from high school, school absenteeism, early resignation from employment, and suicide) are discussed in relation to early life sleep/circadian rhythm patterns. We hypothesize that daily habits of modern society during early stages of life produce unfavorable effects on brain function resulting in problematic behaviors in subsequent years. PMID:24902476

Kohyama, Jun

2014-07-01

251

Adaptation of sleep and circadian rhythms to the Antarctic summer - A question of zeitgeber strength  

NASA Technical Reports Server (NTRS)

Adaptation of sleep and circadian rhythms was examined in three temperate zone dwellers arriving in Antarctica during summer. Rectal temperature, wrist activity, and heart rate were monitored continuously, sleep timing and quality noted on awakening, and mood and fatigue rated every 2 h while awake. Sleep was poorer in 2/3 subjects in Antarctica, where all subjects reported more difficulty rising. Sleep occurred at the same clock times in New Zealand and Antarctica, however, the rhythms of temperature, activity, and heart rate underwent a delay of about of 2 h. The subject with the most Antarctic experience had the least difficulty adapting to sleeping during constant daylight. The subject with the most delayed circadian rhythms had the most difficulty. The delay in the circadian system with respect to sleep and clock time is hypothesized to be due to differences in zeitgeber strength and/or zeitgeber exposure between Antarctica and New Zealand.

Gander, Philippa H.; Macdonald, John A.; Montgomery, John C.; Paulin, Michael G.

1991-01-01

252

[Circadian rhythms and temperature homeostasis in monkeys during a flight on the Kosmos 1514 biosatellite  

NASA Technical Reports Server (NTRS)

In the course of a 5-day space flight of two rhesus-monkeys the following parameters were recorded at an interval of 16 min: core body temperature (Tc), skin temperature (Ts), and motor activity (MA). The telemetric Tc sensor was implanted subcutaneously in the right axilla, Ts thermistor was attached to the right ankle, and the MA piezotape was fixed to the inner side of the vest. Circadian rhythms of Tc varied with a period of 24 hours in one monkey and 25 hours in the other. The daily Tc decreased on the average by 0.5 degrees C, Ts fell immediately after launch and remained close to the lower limit throughout the flight. The Ts amplitude decreased 5-fold. Phases of the circadian rhythms of Ts changed and circadian rhythms of MA remained unchanged and equal to 24 hours.

Klimovitskui, V. Ia; Alpatov, A. M.; Salzman, F. M.; Fuller, C. A.; Moore-Ede, M. S.

1987-01-01

253

Disruption of Circadian Rhythms: A Crucial Factor in the Etiology of Depression  

PubMed Central

Circadian factors might play a crucial role in the etiology of depression. It has been demonstrated that the disruption of circadian rhythms by lighting conditions and lifestyle predisposes individuals to a wide range of mood disorders, including impulsivity, mania and depression. Also, associated with depression, there is the impairment of circadian rhythmicity of behavioral, endocrine, and metabolic functions. Inspite of this close relationship between both processes, the complex relationship between the biological clock and the incidence of depressive symptoms is far from being understood. The efficiency and the timing of treatments based on chronotherapy (e.g., light treatment, sleep deprivation, and scheduled medication) indicate that the circadian system is an essential target in the therapy of depression. The aim of the present review is to analyze the biological and clinical data that link depression with the disruption of circadian rhythms, emphasizing the contribution of circadian desynchrony. Therefore, we examine the conditions that may lead to circadian disruption of physiology and behavior as described in depressive states, and, according to this approach, we discuss therapeutic strategies aimed at treating the circadian system and depression. PMID:21845223

Salgado-Delgado, Roberto; Tapia Osorio, Araceli; Saderi, Nadia; Escobar, Carolina

2011-01-01

254

Disturbed mouse circadian rhythm before the Kobe EQ in 1995  

NASA Astrophysics Data System (ADS)

Legends of macro-anomalies before large earthquakes have been passed down for generations in Asia. Most of the statements on earthquake precursors are considered unreliable afterthoughts by traditional scientists. However, disturbed biological rhythms in mice were observed before the Kobe EQ in 1995 (Yokoi et al, 2003). The records of unusual mouse behavior before the earthquake were obtained to study biological clock at Institute for Protein Research, Osaka University. It is clarified that the disturbance was very rare phenomena statistically. Similar phenomenon was observed before the Wenchuan earthquake in 2008, too (Li et al, 2009). In the presentation, I will discuss the phenomena as one example of preseismic unusual animal behaviors.

Yokoi, Sayoko

2013-04-01

255

Circadian rhythms and mood: Opportunities for multi-level analyses in genomics and neuroscience  

PubMed Central

In the healthy state, both circadian rhythm and mood are stable against perturbations, yet they are capable of adjusting to altered internal cues or ongoing changes in external conditions. The dual demands of stability and flexibility are met by the collective properties of complex neural networks. Disruption of this balance underlies both circadian rhythm abnormality and mood disorders. However, we do not fully understand the network properties that govern the crosstalk between the circadian system and mood regulation. This puzzle reflects a challenge at the center of neurobiology, and its solution requires the successful integration of existing data across all levels of neural organization, from molecules, cells, circuits, network dynamics, to integrated mental function. This essay discusses several open questions confronting the cross-level synthesis, and proposes that circadian regulation, and its role in mood, stands as a uniquely tractable system to study the causal mechanisms of neural adaptation. PMID:24853393

Li, Jun Z

2014-01-01

256

Assaying Locomotor Activity to Study Circadian Rhythms and Sleep Parameters in Drosophila  

PubMed Central

Most life forms exhibit daily rhythms in cellular, physiological and behavioral phenomena that are driven by endogenous circadian (?24 hr) pacemakers or clocks. Malfunctions in the human circadian system are associated with numerous diseases or disorders. Much progress towards our understanding of the mechanisms underlying circadian rhythms has emerged from genetic screens whereby an easily measured behavioral rhythm is used as a read-out of clock function. Studies using Drosophila have made seminal contributions to our understanding of the cellular and biochemical bases underlying circadian rhythms. The standard circadian behavioral read-out measured in Drosophila is locomotor activity. In general, the monitoring system involves specially designed devices that can measure the locomotor movement of Drosophila. These devices are housed in environmentally controlled incubators located in a darkroom and are based on using the interruption of a beam of infrared light to record the locomotor activity of individual flies contained inside small tubes. When measured over many days, Drosophila exhibit daily cycles of activity and inactivity, a behavioral rhythm that is governed by the animal's endogenous circadian system. The overall procedure has been simplified with the advent of commercially available locomotor activity monitoring devices and the development of software programs for data analysis. We use the system from Trikinetics Inc., which is the procedure described here and is currently the most popular system used worldwide. More recently, the same monitoring devices have been used to study sleep behavior in Drosophila. Because the daily wake-sleep cycles of many flies can be measured simultaneously and only 1 to 2 weeks worth of continuous locomotor activity data is usually sufficient, this system is ideal for large-scale screens to identify Drosophila manifesting altered circadian or sleep properties. PMID:20972399

Chiu, Joanna C.; Low, Kwang Huei; Pike, Douglas H.; Yildirim, Evrim; Edery, Isaac

2010-01-01

257

Melatonin secretion is impaired in women with preeclampsia and an abnormal circadian blood pressure rhythm.  

PubMed

Non-dipping circadian blood pressure (BP) is a common finding in preeclampsia, accompanied by adverse outcomes. Melatonin plays pivotal role in biological circadian rhythms. This study investigated the relationship between melatonin secretion and circadian BP rhythm in preeclampsia. Cases were women with preeclampsia treated between January 2006 and June 2007 in the University Hospital of Larissa. Volunteers with normal pregnancy, matched for chronological and gestational age, served as controls. Twenty-four hour ambulatory BP monitoring was applied. Serum melatonin and urine 6-sulfatoxymelatonin levels were determined in day and night time samples by enzyme-linked immunoassays. Measurements were repeated 2 months after delivery. Thirty-one women with preeclampsia and 20 controls were included. Twenty-one of the 31 women with preeclampsia were non-dippers. Compared to normal pregnancy, in preeclampsia there were significantly lower night time melatonin (48.4 ± 24.7 vs. 85.4 ± 26.9 pg/mL, p<0.001) levels. Adjustment for circadian BP rhythm status ascribed this finding exclusively to non-dippers (p<0.01). Two months after delivery, in 11 of the 21 non-dippers both circadian BP and melatonin secretion rhythm reappeared. In contrast, in cases with retained non-dipping status (n=10) melatonin secretion rhythm remained impaired: daytime versus night time melatonin (33.5 ± 13.0 vs. 28.0 ± 13.8 pg/mL, p=0.386). Urinary 6-sulfatoxymelatonin levels were, overall, similar to serum melatonin. Circadian BP and melatonin secretion rhythm follow parallel course in preeclampsia, both during pregnancy and, at least 2 months after delivery. Our findings may be not sufficient to implicate a putative therapeutic effect of melatonin, however, they clearly emphasize that its involvement in the pathogenesis of a non-dipping BP in preeclampsia needs intensive further investigation. PMID:24932757

Bouchlariotou, Sofia; Liakopoulos, Vassilios; Giannopoulou, Myrto; Arampatzis, Spyridon; Eleftheriadis, Theodoros; Mertens, Peter R; Zintzaras, Elias; Messinis, Ioannis E; Stefanidis, Ioannis

2014-08-01

258

Self-arrangement of cellular circadian rhythms through phase-resetting in plant roots  

NASA Astrophysics Data System (ADS)

We discovered a striped pattern of gene expression with circadian rhythms in growing plant roots using bioluminescent imaging of gene expression. Our experimental analysis revealed that the stripe wave in the bioluminescent image originated at the root tip and was caused by a continuous phase resetting of circadian oscillations. Some complex stripe waves containing arrhythmic regions were also observed. We succeeded in describing the formation mechanisms of these patterns using a growing phase oscillator network with a phase-resetting boundary condition.

Fukuda, Hirokazu; Ukai, Kazuya; Oyama, Tokitaka

2012-10-01

259

Seasonal effects on the freerunning rhythm of circadian activity of longnose dace ( Rhinichthys cataractae )  

Microsoft Academic Search

Synopsis Freerunning circadian rhythms of locomotor activity in individual longnose dace sampled from a population at 41°N latitude were recorded under constant darkness throughout the year. There was an annual cycle in the length of the circadian period, with maximum and minimum lengths of mean period of 23.6 and 21.6 h recorded during summer (June) and winter (December), respectively. These

Martin Kavaliers

1981-01-01

260

Regulation of Drosophila circadian rhythms by miRNA let-7 is mediated by a regulatory cycle.  

PubMed

MicroRNA-mediated post-transcriptional regulations are increasingly recognized as important components of the circadian rhythm. Here we identify microRNA let-7, part of the Drosophila let-7-Complex, as a regulator of circadian rhythms mediated by a circadian regulatory cycle. Overexpression of let-7 in clock neurons lengthens circadian period and its deletion attenuates the morning activity peak as well as molecular oscillation. Let-7 regulates the circadian rhythm via repression of CLOCKWORK ORANGE (CWO). Conversely, upregulated cwo in cwo-expressing cells can rescue the phenotype of let-7-Complex overexpression. Moreover, circadian prothoracicotropic hormone (PTTH) and CLOCK-regulated 20-OH ecdysteroid signalling contribute to the circadian expression of let-7 through the 20-OH ecdysteroid receptor. Thus, we find a regulatory cycle involving PTTH, a direct target of CLOCK, and PTTH-driven miRNA let-7. PMID:25417916

Chen, Wenfeng; Liu, Zhenxing; Li, Tianjiao; Zhang, Ruifeng; Xue, Yongbo; Zhong, Yang; Bai, Weiwei; Zhou, Dasen; Zhao, Zhangwu

2014-01-01

261

Circadian rhythms of crawling and swimming in the nudibranch mollusc Melibe leonina.  

PubMed

Daily rhythms of activity driven by circadian clocks are expressed by many organisms, including molluscs. We initiated this study, with the nudibranch Melibe leonina, with four goals in mind: (1) determine which behaviors are expressed with a daily rhythm; (2) investigate which of these rhythmic behaviors are controlled by a circadian clock; (3) determine if a circadian clock is associated with the eyes or optic ganglia of Melibe, as it is in several other gastropods; and (4) test the hypothesis that Melibe can use extraocular photoreceptors to synchronize its daily rhythms to natural light-dark cycles. To address these goals, we analyzed the behavior of 55 animals exposed to either artificial or natural light-dark cycles, followed by constant darkness. We also repeated this experiment using 10 animals that had their eyes removed. Individuals did not express daily rhythms of feeding, but they swam and crawled more at night. This pattern of locomotion persisted in constant darkness, indicating the presence of a circadian clock. Eyeless animals also expressed a daily rhythm of locomotion, with more locomotion at night. The fact that eyeless animals synchronized their locomotion to the light-dark cycle suggests that they can detect light using extraocular photoreceptors. However, in constant darkness, these rhythms deteriorated, suggesting that the clock neurons that influence locomotion may be located in, or near, the eyes. Thus, locomotion in Melibe appears to be influenced by both ocular and extraocular photoreceptors, although the former appear to have a greater influence on the expression of circadian rhythms. PMID:25572214

Newcomb, James M; Kirouac, Lauren E; Naimie, Amanda A; Bixby, Kimberly A; Lee, Colin; Malanga, Stephanie; Raubach, Maureen; Watson, Winsor H

2014-12-01

262

Circadian Rhythms of PER2::LUC in Individual Primary Mouse Hepatocytes and Cultures  

PubMed Central

Background Hepatocytes, the parenchymal cells of the liver, express core clock genes, such as Period2 and Cryptochrome2, which are involved in the transcriptional/translational feedback loop of the circadian clock. Whether or not the liver is capable of sustaining rhythms independent of a central pacemaker is controversial. Whether and how circadian information may be shared among cells in the liver in order to sustain oscillations is currently unknown. Results In this study we isolated primary hepatocytes from transgenic Per2Luc mice and used bioluminescence as a read-out of the state of the circadian clock. Hepatocytes cultured in a collagen gel sandwich configuration exhibited persistent circadian rhythms for several weeks. The amplitude of the rhythms damped, but medium changes consistently reset the phase and amplitude of the cultures. Cry2?/? Per2Luc cells oscillated robustly and expressed a longer period. Co-culturing with wildtype cells did not significantly shorten the period, indicating that coupling among hepatocytes is insufficient to synchronize cells with significantly differing periods. However, spatial patterns revealed by cellular imaging of wildtype cultures provided evidence of weak local coupling among the hepatocytes. Conclusions Our results with primary hepatocyte cultures demonstrate that cultured hepatocytes are weakly coupled. While this coupling is not sufficient to sustain global synchrony, it does increase local synchrony, which may stabilize the circadian rhythms of peripheral oscillators, such as the liver, against noise in the entraining signals. PMID:24498336

Molyneux, Penny C.; Yu, Jimmy K.; Li, Alexander S.; Leise, Tanya L.; Harrington, Mary E.

2014-01-01

263

Circadian Rhythm Hypotheses of Mixed Features, Antidepressant Treatment Resistance, and Manic Switching in Bipolar Disorder  

PubMed Central

Numerous hypotheses have been put forth over the years to explain the development of bipolar disorder. Of these, circadian rhythm hypotheses have gained much importance of late. While the hypothalamus-pituitary-adrenal (HPA) axis hyperactivation hypothesis and the monoamine hypothesis somewhat explain the pathogenic mechanism of depression, they do not provide an explanation for the development of mania/hypomania. Interestingly, all patients with bipolar disorder display significant disruption of circadian rhythms and sleep/wake cycles throughout their mood cycles. Indeed, mice carrying the Clock gene mutation exhibit an overall behavioral profile that is similar to human mania, including hyperactivity, decreased sleep, lowered depression-like behavior, and lower anxiety. It was recently reported that monoamine signaling is in fact regulated by the circadian system. Thus, circadian rhythm instability, imposed on the dysregulation of HPA axis and monoamine system, may in turn increase individual susceptibility for switching from depression to mania/hypomania. In addition to addressing the pathophysiologic mechanism underlying the manic switch, circadian rhythm hypotheses can explain other bipolar disorder-related phenomena such as treatment resistant depression and mixed features. PMID:24302944

Son, Gi-Hoon; Geum, Dongho

2013-01-01

264

Sirtuins, Melatonin and Circadian Rhythms: Building a Bridge between Aging and Cancer  

PubMed Central

Histone deacetylases (HDACs) have been under intense scientific investigation for a number of years. However, only recently the unique class III HDACs, sirtuins, have gained increasing investigational momentum. Originally linked to longevity in yeast, sirtuins and more specifically, SIRT1 have been implicated in numerous biological processes having both protective and/or detrimental effects. SIRT1 appears to play a critical role in the process of carcinogenesis, especially in age-related neoplasms. Similarly, alterations in circadian rhythms as well as production of the pineal hormone melatonin have been linked to aging and cancer risk. Melatonin has been found act as a differentiating agent in some cancer cells and to lower their invasive and metastatic status. In addition, melatonin synthesis and release occurs in a circadian rhythm fashion and it has been linked to the core circadian machinery genes (Clock, Bmal1, Periods, and Cryptochromes). Melatonin has also been associated with chronotherapy, the timely administration of chemotherapy agents to optimize trends in biological cycles. Interestingly, a recent set of studies have linked SIRT1 to the circadian rhythm machinery through direct deacetylation activity as well as through the NAD+ salvage pathway. In this review, we provide evidence for a possible connection between sirtuins, melatonin, and the circadian rhythm circuitry and their implications in aging, chronomodulation and cancer. PMID:20025641

Jung-Hynes, Brittney; Reiter, Russel J.; Ahmad, Nihal

2010-01-01

265

Circadian rhythm of leaf movement in Capsicum annuum observed during centrifugation  

NASA Technical Reports Server (NTRS)

Plant circadian rhythms of leaf movement in seedlings of the pepper plant (Capsicum annuum L., var. Yolo Wonder) were observed at different g-levels by means of a centrifuge. Except for the chronically imposed g-force all environmental conditions to which the plants were exposed were held constant. The circadian period, rate of change of amplitude of successive oscillations, symmetry of the cycles, and phase of the rhythm all were found not to be significantly correlated with the magnitude of the sustained g-force.

Chapman, D. K.; Brown, A. H.; Dahl, A. O.

1975-01-01

266

Dim Light at Night Disrupts Molecular Circadian Rhythms and Affects Metabolism  

PubMed Central

With the exception of high latitudes, life has evolved under bright days and dark nights. Most organisms have developed endogenously driven circadian rhythms which are synchronized to this daily light/dark cycle. In recent years, humans have shifted away from the naturally occurring solar light cycle in favor of artificial and sometimes irregular light schedules produced by electrical lighting. Exposure to unnatural light cycles is increasingly associated with obesity and metabolic syndrome; however the means by which environmental lighting alters metabolism are poorly understood. Thus, we exposed mice to nighttime light and investigated changes in the circadian system and body weight. Here we report that exposure to ecologically relevant levels of dim (5 lux) light at night attenuate core circadian clock rhythms in the SCN at both the gene and protein level. Moreover, circadian clock rhythms were perturbed in the liver by nighttime light exposure. Changes in the circadian clock were associated with temporal alterations in feeding behavior and increased weight gain. These results are significant because they provide mechanistic evidence for how mild changes in environmental lighting can alter circadian and metabolic function. PMID:23929553

Fonken, Laura K.; Aubrecht, Taryn G.; Meléndez-Fernández, O. Hecmarie; Weil, Zachary M.; Nelson, Randy J.

2014-01-01

267

Contribution of the rest-activity circadian rhythm to quality of life in cancer patients.  

PubMed

Quality of life (QoL) is estimated from patients scores to items related to everyday life, including rest and activity. The rest-activity rhythm reflects endogenous circadian clock function. The relation between the individual rhythm in activity and QoL was investigated in 200 patients with metastatic colorectal cancer. Patients wore a wrist actigraph (Ambulatory Monitoring Inc., New York. NY) for 3-5 d before chronotherapy, and completed a QoL questionnaire developed by the European Organization for Research and Treatment of Cancer (QLQ-C30) plus the Hospital Anxiety and Depression Scale. The rest-activity circadian rhythm was characterized by the mean activity level (m), autocorrelation coefficient at 24h (r24), and the dichotomy index (I < O). a ratio between the amount of activity while in and out of bed. The distribution of the rest-activity cycle parameters and that of QoL scores was independent of sex, age, primary tumor, number of metastatic sites, and prior treatment. Both the 24h rhythm indicators were positively correlated with global QoL score as well as physical, emotional, and social functioning. Negative correlations were found between m, r24, or I < O and fatigue, appetite loss, and nausea. The rest-activity circadian rhythm appeared to be an objective indicator of physical welfare and QoL. This analysis suggests that circadian function may be one of the biological determinants of QoL in cancer patients. PMID:11962684

Mormont, Marie-Christine; Waterhouse, Jim

2002-01-01

268

Review article Circadian clocks -from genes to complex behaviour  

E-print Network

Review article Circadian clocks - from genes to complex behaviour Till Roenneberg Martha Merrow (Received 4 February 1999; accepted 16 April 1999) Abstract - Circadian clocks control temporal structure, molecular mechanisms that underlie this endogenous temporal programme. The generation of circadian rhythms

Paris-Sud XI, Université de

269

Circadian rhythms of body temperature and metabolic rate in naked mole-rats  

Microsoft Academic Search

Body temperature (Tb) and metabolic rate (O2 consumption) were measured continuously in naked mole-rats. Circadian rhythms were observed for both parameters. Body temperature increased at the end of the light phase in a 12L:12D cycle in three of four animals. The remaining animal exhibited a freerunning rhythm of Tb. When animals had access to running wheels, the time of elevated

Alexandra P Riccio; Bruce D Goldman

2000-01-01

270

Comparison of synchronization of primate circadian rhythms by light and food  

NASA Technical Reports Server (NTRS)

It is a well-documented fact that cycles of light and dark (LD) are the major entraining agent or 'zeitgeber' for circadian rhythms and that cycles of eating and fasting (EF) are capable of synchronizing a few circadian rhythms in the squirrel monkey. In this paper, by contrasting how these rhythms are timed by LD and EF cycles, the differential coupling to the oscillating system within adult male squirrel monkeys is examined. The variables measured are the rhythms of drinking, colonic temperature, and urinary potassium and water excretion. Attention is given to a comparison of the reproducibility of the averaged waveforms of the rhythms, the stability of the timing of a phase reference point, and the rate of resynchronization of these rhythms following an abrupt 8-hr phase delay in the zeitgeber. It is shown that the colonic temperature rhythm is more tightly controlled by LD than EF cycles, and that the drinking and urinary rhythms are more tightly coupled to EF than LD cycles.

Sulzman, F. M.; Fuller, C. A.; Moore-Ede, M. C.

1978-01-01

271

Influence of the circadian rhythm in cell division on radiation-induced mitotic delay in vivo  

SciTech Connect

Mitotic delay is described as a classical response to radiation; however, circadian rhythmicity in cell division in vivo has not been considered by many authors. The present study investigated the relation between fluctuations reported as mitotic delay and recovery in vivo and circadian oscillations in mitotic index in mouse corneal epithelium. One aspect involved single doses (approximately 600 rad) given to mice at different circadian stages. The normal circadian rhythm in cell division was never obliterated. Inhibition of mitosis was evident but unpredictable, ranging from 6 to 15 hr after irradiation. Recovery was evident only during the daily increase in mitotic index of controls. The classical interpretation of recovery from mitotic delay may be in an in vitro phenomenon not reflecting in vivo responses, which are apparently strongly circadian stage dependent. The second portion of the study demonstrated a dose-response effect on length of mitotic delay and, to a lesser extent, degree of recovery.

Rubin, N.H.

1982-01-01

272

Circadian rhythm disruption was observed in hand, foot, and mouth disease patients.  

PubMed

Hand, foot, and mouth disease (HFMD) with central nerve system complications may rapidly progress to fulminated cardiorespiratory failure, with higher mortality and worse prognosis. It has been reported that circadian rhythms of heart rate (HR) and respiratory rate are useful in predicting prognosis of severe cardiovascular and neurological diseases. The present study aims to investigate the characteristics of the circadian rhythms of HR, respiratory rate, and temperature in HFMD patients with neurological complications.Hospitalized HFMD patients including 33 common cases (common group), 61 severe cases (severe group), and 9 critical cases (critical group) were contrasted retrospectively. Their HR, respiratory rate, and temperatures were measured every 4 hours during the first 48-hour in the hospital. Data were analyzed with the least-squares fit of a 24-hour cosine function by the single cosinor and population-mean cosinor method.Results of population-mean cosinor analysis demonstrated that the circadian rhythm of HR, respiratory rate, and temperature was present in the common and severe group, but absent in the critical group. The midline-estimating statistic of rhythm (MESOR) (P?=?0.016) and acrophase (P?circadian characteristics of HR among 3 groups. Compared with the common group, the MESOR of temperature and respiratory rate was significantly higher, and acrophase of temperature and respiratory rate was 2 hours ahead in the severe group, critical HFMD patients lost their population-circadian rhythm of temperature, HR, and respiratory rate. The high values of temperature and respiratory rate for the common group were concentrated between 3 and 9 PM, whereas those for the severe group were more dispersive. And the high values for the critical group were equally distributed in 24 hours of the day.Circadian rhythm of patients' temperature in the common group was the same as the normal rhythm of human body temperature. Circadian rhythm of patients' temperature, HR and respiratory rate in 3 groups were significantly different. PMID:25761178

Zhu, Yu; Jiang, Zhou; Xiao, Guoguang; Cheng, Suting; Wen, Yang; Wan, Chaomin

2015-03-01

273

Circadian rhythms and endocrine functions in adult insects.  

PubMed

Many behavioral and physiological processes in adult insects are influenced by both the endocrine and circadian systems, suggesting that these two key physiological systems interact. We reviewed the literature and found that experiments explicitly testing these interactions in adult insects have only been conducted for a few species. There is a shortage of measurements of hormone titers throughout the day under constant conditions even for the juvenile hormones (JHs) and ecdysteroids, the best studied insect hormones. Nevertheless, the available measurements of hormone titers coupled with indirect evidence for circadian modulation of hormone biosynthesis rate, and the expression of genes encoding proteins involved in hormone biosynthesis, binding or degradation are consistent with the hypothesis that the circulating levels of many insect hormones are influenced by the circadian system. Whole genome microarray studies suggest that the modulation of farnesol oxidase levels is important for the circadian regulation of JH biosynthesis in honey bees, mosquitoes, and fruit flies. Several studies have begun to address the functional significance of circadian oscillations in endocrine signaling. The best understood system is the circadian regulation of Pheromone Biosynthesis Activating Neuropeptide (PBAN) titers which is important for the temporal organization of sexual behavior in female moths. The evidence that the circadian and endocrine systems interact has important implications for studies of insect physiology and behavior. Additional studies on diverse species and physiological processes are needed for identifying basic principles underlying the interactions between the circadian and endocrine systems in insects. PMID:23103982

Bloch, Guy; Hazan, Esther; Rafaeli, Ada

2013-01-01

274

Modeling the influence of circadian rhythms on the acute inflammatory response  

E-print Network

(Angus et al., 2001). Thus, the management of inflammation is a major challenge in the treatment Inflammation PK/PD modeling Signaling and regulation Circadian rhythms a b s t r a c t A wide variety of modeling techniques have been applied towards understanding inflammation. These models have broad potential

Androulakis, Ioannis (Yannis)

275

Melatonin, sleep, and circadian rhythms: rationale for development of specific melatonin agonists  

E-print Network

Review Melatonin, sleep, and circadian rhythms: rationale for development of specific melatonin of the population. A feature common among CRSDs and some forms of insomnia is sensitivity to the hormone melatonin, which is secreted by the pineal gland. Accumulating evidence suggests that melatonin may regulate

Gillette, Martha U.

276

Free-running circadian activity rhythms in free-living beaver ( Castor canadensis )  

Microsoft Academic Search

The members of a beaver family studied under natural conditions in SW Alberta, Canada (115 °03' W, 51 °02' N) displayed a free-running circadian rhythm of activity with a period length of about 27 hours in winter, at a time when they were living under ice and had no access to land (Fig. 1, A and C). In summer, the

Jacques Bovet; Erwin F. Oertli

1974-01-01

277

The disconnected Visual System Mutations in Drosophila melanogaster Drastically Disrupt Circadian Rhythms  

Microsoft Academic Search

Mutations at the disconnected (disco) locus in Drosophila melanogaster cause cultures of this insect to eclose in an essentially arrhythmic manner and also nearly eliminate free-running circadian rhythms of locomotor activity. Yet disco mutants are not totally light- insensitive : Whereas they performed very poorly in tests of certain behavioral responses to visual stimuli, they were able to exhibit \\

Mitchell S. Dushay; Michael Rosbash; Jeffrey C. Hall

1989-01-01

278

Darwin, Earthworms & Circadian Rhythms: A Fertile Field for Science Fair Experiments  

ERIC Educational Resources Information Center

This article discusses why the study of earthworms has fascinated many scientists, and why earthworms make ideal experimental animals for students to test in the laboratory. Although earthworms may appear to be primitive, they are governed by both circadian and seasonal rhythms, just as more advanced organisms are. They possess an intelligence…

Burns, John T.; Scurti, Paul J.; Furda, Amy M.

2009-01-01

279

Effects of pinealectomy on circadian locomotor activity rhythms in european starlings, Sturnus vulgaris  

Microsoft Academic Search

Removal of the pineal organ from starlings had drastic effects on their freerunning circadian activity rhythms; in birds kept in continuous darkness the period (t) shortened and the activity time (a) lengthened. Concomitantly botht anda became relatively unstable and the separation between activity and rest time was obscured. In a few birds activity became continuous and apparently arrhythmic. The activity

Eberhard Gwinner

1978-01-01

280

Assessing circadian rhythms in propofol PK and PD during prolonged infusion in ICU patients  

PubMed Central

This study evaluates possible circadian rhythms during prolonged propofol infusion in patients in the intensive care unit. Eleven patients were sedated with a constant propofol infusion. The blood samples for the propofol assay were collected every hour during the second day, the third day, and after the termination of the propofol infusion. Values of electroencephalographic bispectral index (BIS), arterial blood pressure, heart rate, blood oxygen saturation and body temperature were recorded every hour at the blood collection time points. A two-compartment model was used to describe propofol pharmacokinetics. Typical values of the central and peripheral volume of distribution and inter-compartmental clearance were VC = 27.7 l, VT = 801 l, and CLD = 2.73 l/min. The systolic blood pressure (SBP) was found to influence the propofol metabolic clearance according to Cl (l/min) = 2.65·(1 ? 0.00714·(SBP ? 135)). There was no significant circadian rhythm detected with respect to propofol pharmacokinetics. The BIS score was assessed as a direct effect model with EC50 equal 1.98 mg/l. There was no significant circadian rhythm detected within the BIS scores. We concluded that the light–dark cycle did not influence propofol pharmacokinetics and pharmacodynamics in intensive care units patients. The lack of night–day differences was also noted for systolic blood pressure, diastolic blood pressure and blood oxygenation. Circadian rhythms were detected for heart rate and body temperature, however they were severely disturbed from the pattern of healthy patients. PMID:20544262

Kusza, Krzysztof; Wawrzyniak, Katarzyna; Grze?kowiak, Edmund; Kokot, Zenon J.; Matysiak, Jan; Grabowski, Tomasz; Wolc, Anna; Wiczling, Pawe?; Regulski, Mi?osz

2010-01-01

281

Long-Term Fitness Training Improves the Circadian Rest-Activity Rhythm in Healthy Elderly Males  

Microsoft Academic Search

In old age, the circadian timing system loses optimal functioning. This process is even accelerated in Alzheimer's disease. Because pharmacological treatment of day-night rhythm disturbances usually is not very effective and may have considerable side effects, nonpharmacological treatments deserve attention. Bright light therapy has been shown to be effective. It is known from animal studies that increased activity, or an

Eus J. W. Van Someren; Cees Lijzenga; Majid Mirmiran; Dick F. Swaab

1997-01-01

282

Relationships between circadian rhythms and modulation of gene expression by glucocorticoids in skeletal muscle  

PubMed Central

The existence and maintenance of biological rhythms linked to the 24-h light-dark cycle are essential to the health and functioning of an organism. Although much is known concerning central clock mechanisms, much less is known about control in peripheral tissues. In this study, circadian regulation of gene expression was examined in rat skeletal muscle. A rich time series involving 54 animals euthanized at 18 distinct time points within the 24-h cycle was performed, and mRNA expression in gastrocnemius muscles was examined using Affymetrix gene arrays. Data mining identified 109 genes that were expressed rhythmically, which could be grouped into eight distinct temporal clusters within the 24-h cycle. These genes were placed into 11 functional categories, which were examined within the context of temporal expression. Transcription factors involved in the regulation of central rhythms were examined, and eight were found to be rhythmically expressed in muscle. Because endogenous glucocorticoids are a major effector of circadian rhythms, genes identified here were compared with those identified in previous studies as glucocorticoid regulated. Of the 109 genes identified here as circadian rhythm regulated, only 55 were also glucocorticoid regulated. Examination of transcription factors involved in circadian control suggests that corticosterone may be the initiator of their rhythmic expression patterns in skeletal muscle. PMID:18667713

Almon, Richard R.; Yang, Eric; Lai, William; Androulakis, Ioannis P.; Ghimbovschi, Svetlana; Hoffman, Eric P.; Jusko, William J.; DuBois, Debra C.

2008-01-01

283

A Mutant Drosophila Homolog of Mammalian Clock Disrupts Circadian Rhythms and Transcription of period and timeless  

Microsoft Academic Search

We report the identification, characterization, and cloning of a novel Drosophila circadian rhythm gene, dClock. The mutant, initially called Jrk, manifests dominant effects: heterozygous flies have a period alteration and half are arrhythmic, while homozygous flies are uniformly arrhythmic. Furthermore, these flies express low levels of the two clock proteins, PERIOD (PER) and TIMELESS (TIM), due to low per and

Ravi Allada; Neal E White; W. Venus So; Jeffrey C Hall; Michael Rosbash

1998-01-01

284

Loss of Circadian Behavioral Rhythms and per RNA Oscillations in the Drosophila Mutant timeless  

Microsoft Academic Search

Eclosion, or emergence of adult flies from the pupa, and locomotor activity of adults occur rhythmically in Drosophila melanogaster, with a circadian period of about 24 hours. Here, a clock mutation, timeless (tim), is described that produces arrhythmia for both behaviors. The effects of tim on behavioral rhythms are likely to involve products of the X chromosome-linked clock gene period

Amita Sehgal; Jeffrey L. Price; Bernice Man; Michael W. Young

1994-01-01

285

Maternal obesity and post-natal high fat diet disrupt hepatic circadian rhythm in rat offspring  

Technology Transfer Automated Retrieval System (TEKTRAN)

Offspring of obese (Ob) rat dams gain greater body wt and fat mass when fed high-fat diet (HFD) as compared to controls. Alterations of diurnal circadian rhythm are known to detrimentally impact metabolically active tissues such as liver. We sought to determine if maternal obesity (MOb) leads to p...

286

A Comparative Study of Circadian Rhythm Functioning and Sleep in People with Asperger Syndrome  

ERIC Educational Resources Information Center

The circadian rhythm functioning and sleep patterns of 10 adults with Asperger syndrome were investigated using actigraphy. When compared with data from neurotypical adults, both statistical and clinically significant differences were found between the two groups, with the adults with Asperger syndrome showing marked abnormalities in both the…

Hare, Dougal Julian; Jones, Steven; Evershed, Kate

2006-01-01

287

CIRCADIAN RHYTHMS OF FEEDING, OVIPOSITION, AND EMERGENCE OF THE BOLL WEEVIL (COLEOPTERA: CURCULIONIDAE)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Circadian rhythm of feeding, oviposition, and emergence of boll weevil adults were determined at 5 different photophases (24, 14, 12, 10 and 0 hours) and a constant 27 deg C temperature, 65% RH in the laboratory. Squares from petri dishes, where they were exposed to boll weevil females, were remove...

288

Pulses of darkness shift the phase of a circadian rhythm in an insectivorous bat  

Microsoft Academic Search

Summary The circadian rhythm of a tropical insectivorous bat,Taphozous melanopogon, free-runs in dim light and responds to dark breaks of a few hours' duration with ‘advances’ and ‘delays’ as a function of the phase experiencing the “black out”. Similarly phase shifts also follow perturbations by light breaks. The time course and the wave form of the phase response curves obtained

Ramanujam Subbaraj; Maroli K. Chandrashekaran

1978-01-01

289

Multiple Amidated Neuropeptides Are Required for Normal Circadian Locomotor Rhythms in Drosophila  

Microsoft Academic Search

In Drosophila, the amidated neuropeptide pigment dispersing factor (PDF) is expressed by the ventral subset of lateral pace- maker neurons and is required for circadian locomotor rhythms. Residual rhythmicity in pdf mutants likely reflects the activity of other neurotransmitters. We asked whether other neuropep- tides contribute to such auxiliary mechanisms. We used the gal4\\/UAS system to create mosaics for the

Paul H. Taghert; Randall S. Hewes; Jae H. Park; Martha A. O'Brien; Mei Han; Molly E. Peck

2001-01-01

290

Melatonin, sleep, and circadian rhythms: rationale for development of specific melatonin agonists  

Microsoft Academic Search

Circadian rhythm sleep disorders (CRSDs), whether chronic or transient, affect a broad range of individuals, including many elderly, those with severe visual impairments, shift workers, and jet travelers moving rapidly across many time zones. In addition, various forms of insomnia affect another large sector of the population. A feature common among CRSDs and some forms of insomnia is sensitivity to

Fred W. Turek; Martha U. Gillette

2004-01-01

291

Effect of feeding regimens on circadian rhythms: implications for aging and longevity.  

PubMed

Increased longevity and improved health can be achieved in mammals by two feeding regimens, caloric restriction (CR), which limits the amount of daily calorie intake, and intermittent fasting (IF), which allows the food to be available ad libitum every other day. The precise mechanisms mediating these beneficial effects are still unresolved. Resetting the circadian clock is another intervention that can lead to increased life span and well being, while clock disruption is associated with aging and morbidity. Currently, a large body of evidence links circadian rhythms with metabolism and feeding regimens. In particular, CR, and possibly also IF, can entrain the master clock located in the suprachiasmatic nuclei (SCN) of the brain hypothalamus. These findings raise the hypothesis that the beneficial effects exerted by these feeding regimens could be mediated, at least in part, through resetting of the circadian clock, thus leading to synchrony in metabolism and physiology. This hypothesis is reinforced by a transgenic mouse model showing spontaneously reduced eating alongside robust circadian rhythms and increased life span. This review will summarize recent findings concerning the relationships between feeding regimens, circadian rhythms, and metabolism with implications for ageing attenuation and life span extension. PMID:20228939

Froy, Oren; Miskin, Ruth

2010-01-01

292

Circadian Mechanisms of Food Anticipatory Rhythms in Rats Fed Once or Twice Daily: Clock Gene and Endocrine Correlates  

PubMed Central

Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12?12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times. After 30 days, brain, blood, adrenal and stomach tissue were collected at 6 time points. Multiple clock genes from adrenals and stomachs were assayed by RT-PCR. Blood was assayed for corticosterone and ghrelin. Bmal1 expression was quantified in 14 brain regions by in situ hybridization. Clock gene rhythms in adrenal and stomach from day-fed rats oscillated in antiphase with the rhythms in night-fed rats, and at an intermediate phase in rats fed twice daily. Corticosterone and ghrelin in 1-meal rats peaked at or prior to the expected mealtime. In 2-meal rats, corticosterone peaked only prior the nighttime meal, while ghrelin peaked prior to the daytime meal and then remained elevated. The olfactory bulb, nucleus accumbens, dorsal striatum, cerebellum and arcuate nucleus exhibited significant daily rhythms of Bmal1 in the night-fed groups that were approximately in antiphase in the day-fed groups, and at intermediate levels (arrhythmic) in rats anticipating 2 daily meals. The dissociations between anticipatory activity and the peripheral clocks and hormones in rats anticipating 2 daily meals argue against a role for these signals in the timing of behavioral rhythms. The absence of rhythmicity at the tissue level in brain regions from rats anticipating 2 daily meals support behavioral evidence that circadian clock cells in these tissues may reorganize into two populations coupled to different meals. PMID:25502949

Patton, Danica F.; Katsuyama, Ângela M.; Pavlovski, Ilya; Michalik, Mateusz; Patterson, Zachary; Parfyonov, Maksim; Smit, Andrea N.; Marchant, Elliott G.; Chung, John; Abizaid, Alfonso; Storch, Kai-Florian; de la Iglesia, Horacio; Mistlberger, Ralph E.

2014-01-01

293

The circadian clock controls the expression pattern of the circadian input photoreceptor, phytochrome B  

E-print Network

The circadian clock controls the expression pattern of the circadian input photoreceptor responses, including most light responses, also are mod- ulated by circadian rhythms that are generated by an endogenous oscillator, the circadian clock. To provide information on local time, circadian clocks

Millar, Andrew J.

294

Circadian Activity Rhythms and Sleep in Nurses Working Fixed 8-hr Shifts.  

PubMed

Shift work is associated with adverse health outcomes. The aim of this study was to explore the effects of shift work on circadian activity rhythms (CARs) and objective and subjective sleep quality in nurses. Female day-shift (n = 16), evening-shift (n = 6), and night-shift (n = 13) nurses wore a wrist actigraph to monitor the activity. We used cosinor analysis and time-frequency analysis to study CARs. Night-shift nurses exhibited the lowest values of circadian rhythm amplitude, acrophase, autocorrelation, and mean of the circadian relative power (CRP), whereas evening-shift workers exhibited the greatest standard deviation of the CRP among the three shift groups. That is, night-shift nurses had less robust CARs and evening-shift nurses had greater variations in CARs compared with nurses who worked other shifts. Our results highlight the importance of assessing CARs to prevent the adverse effects of shift work on nurses' health. PMID:25332463

Kang, Jiunn-Horng; Miao, Nae-Fang; Tseng, Ing-Jy; Sithole, Trevor; Chung, Min-Huey

2014-10-20

295

Circadian rhythm mutations in Drosophila melanogaster affect short-term fluctuations in the male's courtship song.  

PubMed Central

Courtship song in Drosophila is produced by the male's wing vibration and consists of pulses of tone produced at intervals of approximately 34 msec in D. melanogaster and 48 msec in D. simulans. We have observed that the intervals between these pulses are not constant but fluctuate rhythmically with periods of approximately 1 min in D. melanogaster and 0.5 min in D. simulans. In D. melanogaster, three allelic per mutations have been isolated which affect the periodicity of the circadian oscillators affecting both eclosion and locomotor activity [Konopka, R. & Benzer S. (1971) Proc. Natl. Acad. Sci. USA 68, 2112-2116]. Each of the per alleles--pers, which shortens the circadian period, perI, which lengthens it, and perO, which abolishes it--strikingly affects the 60-sec song rhythm in a parallel fashion. Therefore, both circadian rhythms and a very short, noncircadian oscillation appear to be influenced by the same gene. PMID:6779281

Kyriacou, C P; Hall, J C

1980-01-01

296

A computational model for functional mapping of genes that regulate intra-cellular circadian rhythms  

PubMed Central

Background Genes that control circadian rhythms in organisms have been recognized, but have been difficult to detect because circadian behavior comprises periodically dynamic traits and is sensitive to environmental changes. Method We present a statistical model for mapping and characterizing specific genes or quantitative trait loci (QTL) that affect variations in rhythmic responses. This model integrates a system of differential equations into the framework for functional mapping, allowing hypotheses about the interplay between genetic actions and periodic rhythms to be tested. A simulation approach based on sustained circadian oscillations of the clock proteins and their mRNAs has been designed to test the statistical properties of the model. Conclusion The model has significant implications for probing the molecular genetic mechanism of rhythmic oscillations through the detection of the clock QTL throughout the genome. PMID:17261199

Liu, Tian; Liu, Xueli; Chen, Yunmei; Wu, Rongling

2007-01-01

297

Circadian rhythm of the cyanobacterium Synechocystis sp. strain PCC 6803 in the dark.  

PubMed Central

The cyanobacterium Synechocystis sp. strain PCC 6803 exhibited circadian rhythms in complete darkness. To monitor a circadian rhythm of the Synechocystis cells in darkness, we introduced a PdnaK1::luxAB gene fusion (S. Aoki, T. Kondo, and M. Ishiura, J. Bacteriol. 177:5606-5611, 1995), which was composed of a promoter region of the Synechocystis dnaK1 gene and a promoterless bacterial luciferase luxAB gene set, as a reporter into the chromosome of a dark-adapted Synechocystis strain. The resulting dnaK1-reporting strain showed bioluminescence rhythms with a period of 25 h (on agar medium supplemented with 5 mM glucose) for at least 7 days in darkness. The rhythms were reset by 12-h-light-12-h-dark cycles, and the period of the rhythms was temperature compensated for between 24 and 31 degrees C. These results indicate that light is not necessary for the oscillation of the circadian clock in Synechocystis. PMID:9294431

Aoki, S; Kondo, T; Wada, H; Ishiura, M

1997-01-01

298

Drosophila TRPA1 functions in temperature control of circadian rhythm in pacemaker neurons  

PubMed Central

Most animals from flies to humans count on circadian clocks to synchronize their physiology and behaviors. Daily light cycles are well-known environmental cues for setting circadian rhythms. Warmer and cooler temperatures that mimic day and night are also effective in entraining circadian activity in most animals. Even vertebrate organisms can be induced to show circadian responses through exposure to temperature cycles. In poikilothermic animals such as Drosophila, temperature differences of only 2–3°C are sufficient to synchronize locomotor rhythms. However, the molecular sensors that participate in temperature regulation of circadian activity in fruit flies or other animals are enigmatic. It is also unclear whether such detectors are limited to the periphery or may be in the central brain. Here, we showed that Drosophila TRPA1 (Transient Receptor Potential Cation Channel A1) was necessary for normal activity patterns during temperature cycles. The trpA1 gene was expressed in a subset of pacemaker neurons in the central brain. In response to temperature entrainment, loss of trpA1 impaired activity, and altered expression of the circadian clock protein Period (Per) in a subset of pacemaker neurons. These findings underscore a role for a thermoTRP in temperature regulation that extends beyond avoidance of noxious or suboptimal temperatures. PMID:23595730

Lee, Youngseok; Montell, Craig

2013-01-01

299

Circadian rhythm in gastric mucosal blood flow in fasting rat stomach.  

PubMed

Circadian rhythms are present in several gastric functions including acid secretion and emptying rates. We hypothesize that aggressive and defensive factors in the gastric mucosa follow similar circadian rhythms. The purpose of this study was to determine if gastric mucosal blood flow, a known defensive factor, manifests a circadian rhythm in fasting rats. Ninety-six male Sprague-Dawley rats were light-adapted in isolation chambers for 3 weeks prior to the study. Half the rats experienced light from 6:00 AM to 6:00 PM, the other half from 6:00 PM to 6:00 AM. After an 18-hr fast, 12 rats were studied at each of eight sampling times: 0100, 0400, 0700, 1000, 1300, 1600, 1900, and 2200 hr after lights on (HALO). After anesthesia and laparotomy, the stomachs were opened along the anterior surface, gently stretched with mucosal surface upmost, and trapped between two lucite rings, with blood supply intact. Mucosal blood flow (ml/min/100 g) was measured in the forestomach, corpus, and antrum with a laser Doppler flowmeter (TSI Laserflo BPM 403). Cosinor analysis showed a significant (P less than 0.01) circadian rhythm in gastric mucosal blood flow within the corpus and antrum, but not in the forestomach. Peak time for corpus blood flow was 21:45 +/- 0:56 HALO (3:45 AM). In the antrum it was 0:51 +/- 1:08 HALO (6:51 AM). These results support the hypothesis that circadian rhythms in mucosal defensive functions are an integral part of normal gastric physiology. PMID:1921365

Larsen, K R; Dayton, M T; Moore, J G

1991-10-01

300

Ontogeny of the rabbit's circadian rhythms without an external zeitgeber  

Microsoft Academic Search

We have monitored parturition and different behavioral rhythms of does, the activity of suckling pups and behavioral rhythms of rabbits after weaning until adulthood. All animals were living in continuous light conditions (LL). As a consequence of the free-run of the does parturition, which takes place during the resting period of the animal, occurred at almost any time of the

Burghart Jilge

1995-01-01

301

Alteration of Daily and Circadian Rhythms following Dopamine Depletion in MPTP Treated Non-Human Primates  

PubMed Central

Disturbances of the daily sleep/wake cycle are common non-motor symptoms of Parkinson's disease (PD). However, the impact of dopamine (DA) depletion on circadian rhythms in PD patients or non-human primate (NHP) models of the disorder have not been investigated. We evaluated alterations of circadian rhythms in NHP following MPTP lesion of the dopaminergic nigro-striatal system. DA degeneration was assessed by in vivo PET ([11C]-PE2I) and post-mortem TH and DAT quantification. In a light?dark cycle, control and MPTP-treated NHP both exhibit rest-wake locomotor rhythms, although DA-depleted NHP show reduced amplitude, decreased stability and increased fragmentation. In all animals, 6-sulphatoxymelatonin peaks at night and cortisol in early morning. When the circadian system is challenged by exposure to constant light, controls retain locomotor rest-wake and hormonal rhythms that free-run with stable phase relationships whereas in the DA-depleted NHP, locomotor rhythms are severely disturbed or completely abolished. The amplitude and phase relations of hormonal rhythms nevertheless remain unaltered. Use of a light-dark masking paradigm shows that expression of daily rest-wake activity in MPTP monkeys requires the stimulatory and inhibitory effects of light and darkness. These results suggest that following DA lesion, the central clock in the SCN remains intact but, in the absence of environmental timing cues, is unable to drive downstream rhythmic processes of striatal clock gene and dopaminergic functions that control locomotor output. These findings suggest that the circadian component of the sleep-wake disturbances in PD is more profoundly affected than previously assumed. PMID:24465981

Fifel, Karim; Vezoli, Julien; Dzahini, Kwamivi; Claustrat, Bruno; Leviel, Vincent; Kennedy, Henry; Procyk, Emmanuel; Dkhissi-Benyahya, Ouria; Gronfier, Claude; Cooper, Howard M.

2014-01-01

302

Circadian rhythms and sleep—the metabolic connection  

Microsoft Academic Search

The circadian system coordinates mammalian physiology and behavior with the environmental light–dark cycle. It allocates sleep\\u000a to the inactivity phase using various mechanisms involving neurotransmitters, nuclear receptors, and protein kinases. These\\u000a pathways are related to metabolism, indicating that the circadian system and sleep are connected via metabolic parameters.\\u000a This suggests that organs other than the brain may “sleep.” A hypothetic

Urs Albrecht

303

The Nuclear Receptor Genes HR3 and E75 Are Required for the Circadian Rhythm in a Primitive Insect  

PubMed Central

Insect circadian rhythms are generated by a circadian clock consisting of transcriptional/translational feedback loops, in which CYCLE and CLOCK are the key elements in activating the transcription of various clock genes such as timeless (tim) and period (per). Although the transcriptional regulation of Clock (Clk) has been profoundly studied, little is known about the regulation of cycle (cyc). Here, we identify the orphan nuclear receptor genes HR3 and E75, which are orthologs of mammalian clock genes, Ror? and Rev-erb?, respectively, as factors involved in the rhythmic expression of the cyc gene in a primitive insect, the firebrat Thermobia domestica. Our results show that HR3 and E75 are rhythmically expressed, and their normal, rhythmic expression is required for the persistence of locomotor rhythms. Their RNAi considerably altered the rhythmic transcription of not only cyc but also tim. Surprisingly, the RNAi of HR3 revealed the rhythmic expression of Clk, suggesting that this ancestral insect species possesses the mechanisms for rhythmic expression of both cyc and Clk genes. When either HR3 or E75 was knocked down, tim, cyc, and Clk or tim and cyc, respectively, oscillated in phase, suggesting that the two genes play an important role in the regulation of the phase relationship among the clock genes. Interestingly, HR3 and E75 were also found to be involved in the regulation of ecdysis, suggesting that they interconnect the circadian clock and developmental processes. PMID:25502221

Kamae, Yuichi; Uryu, Outa; Miki, Taiki; Tomioka, Kenji

2014-01-01

304

Plasticity of circadian activity and body temperature rhythms in golden spiny mice.  

PubMed

Most animals can be categorized as nocturnal, diurnal, or crepuscular. However, rhythms can be quite plastic in some species and vary from one individual to another within a species. In the golden spiny mouse (Acomys russatus), a variety of rhythm patterns have been seen, and these patterns can change considerably as animals are transferred from the field into the laboratory. We previously suggested that these animals may have a circadian time-keeping system that is fundamentally nocturnal and that diurnal patterns seen in their natural habitat reflect mechanisms operating outside of the basic circadian time-keeping system (i.e., masking). In the current study, we further characterized plasticity evident in the daily rhythms of golden spiny mice by measuring effects of lighting conditions and access to a running wheel on rhythms in general activity (GA) and body temperature (Tb). Before the wheel was introduced, most animals were active mainly during the night, though there was considerable inter-individual variability and patterns were quite plastic. The introduction of the wheel caused an increase in the level of nighttime activity and Tb in most individuals. The periods of the rhythms in constant darkness (DD) were very similar, and even slightly longer in this study (24.1+/-0.2 h) than in an earlier one in which animals had not been provided with running wheels. We found no correlation between the distance animals ran in their wheels and the period of their rhythms in DD. Re-entrainment after phase delays of the LD cycle occurred more rapidly in the presence than absence of the running wheel. The characteristics of the rhythms of golden spiny mice seen in this study may be the product of natural selection favoring plasticity of the circadian system, perhaps reflecting what can happen during an evolutionary transition as animals move from a nocturnal to a diurnal niche. PMID:19360488

Cohen, Rotem; Smale, Laura; Kronfeld-Schor, Noga

2009-04-01

305

Circadian rhythms of visual accommodation responses and physiological correlations.  

NASA Technical Reports Server (NTRS)

Use of a recently developed servocontrolled infrared optometer to continuously record the state of monocular focus while subjects viewed a visual target for which the stimulus to focus was systematically varied. Calculated parameters form recorded data - e.g., speeds of accommodation to approaching and receding targets, magnitude of accommodation to step changes in target distance, and amplitude and phase lag of response to sinusoidally varying stimuli were submitted to periodicity analyses. Ear canal temperature (ECT) and heart rate (HR) rhythms were also recorded for physiological correlation with accommodation rhythms. HR demonstrated a 24-hr rhythm, but ECT data did not.

Murphy, M. R.; Randle, R. J.; Williams, B. A.

1972-01-01

306

Circadian rhythms originate from intertwined feedback processes in genetic regulatory net-works. Computational models of increasing complexity have been proposed for the molec-  

E-print Network

ABSTRACT Circadian rhythms originate from intertwined feedback processes in genetic regulatory net for circadian rhythms in Drosophila account for a variety of dynamical properties, such as phase shifting of these models allow us to examine how molecular noise affects the emergence and robustness of circadian

Goldbeter, Albert

307

Circadian rhythms in electric waveform structure and rate in the electric fish Brachyhypopomus pinnicaudatus  

PubMed Central

Weakly electric fish have long been known to express day–night oscillations in their discharge rates, and in the amplitude and duration of individual electric organ discharges (EODs). Because these oscillations are altered by social environment and neuroendocrine interactions, electric fish are excellent organisms for exploring the social and neuroendocrine regulation of circadian rhythm expression. Previous studies asserting that these oscillations are circadian rhythms have been criticized for failing to control temperature and randomize feeding regimes, or for running the fish under constant conditions for just 2–3 days. Here we show that the day–night oscillations in the EODs of the neotropical gymnotiform fish Brachyhypopomus pinnicaudatus free-run for over a week under constant photic and thermal conditions, and randomized food provisioning. Sex differences were apparent in strength and magnitude of the circadian oscillations; male oscillations were stronger and larger. All three parameters retain a common oscillation period while differing in the persistence of oscillation strength and magnitude, a difference consistent with proposals by others that declines of behavioral circadian rhythms may result from breakdowns downstream of the central oscillator. PMID:16996093

Stoddard, Philip K.; Markham, Michael R.; Salazar, Vielka L.; Allee, Susan

2008-01-01

308

Animal activity around the clock with no overt circadian rhythms: patterns, mechanisms and adaptive value  

PubMed Central

Circadian rhythms are ubiquitous in many organisms. Animals that are forced to be active around the clock typically show reduced performance, health and survival. Nevertheless, we review evidence of animals showing prolonged intervals of activity with attenuated or nil overt circadian rhythms and no apparent ill effects. We show that around-the-clock and ultradian activity patterns are more common than is generally appreciated, particularly in herbivores, in animals inhabiting polar regions and habitats with constant physical environments, in animals during specific life-history stages (such as migration or reproduction), and in highly social animals. The underlying mechanisms are diverse, but studies suggest that some circadian pacemakers continue to measure time in animals active around the clock. The prevalence of around-the-clock activity in diverse animals and habitats, and an apparent diversity of underlying mechanisms, are consistent with convergent evolution. We suggest that the basic organizational principles of the circadian system and its complexity encompass the potential for chronobiological plasticity. There may be trade-offs between benefits of persistent daily rhythms versus plasticity, which for reasons still poorly understood make overt daily arrhythmicity functionally adaptive only in selected habitats and for selected lifestyles. PMID:23825202

Bloch, Guy; Barnes, Brian M.; Gerkema, Menno P.; Helm, Barbara

2013-01-01

309

348 Brain Research, 474(1988)348-352 Circadian rhythm of the rat suprachiasmatic brain slice is  

E-print Network

: Brainslice;cAMP;Circadianrhythm;Hypothalamus;Oscillator;Pacemaker;Phase-shift;Suprachiasmaticnuclei Cellular phaseofthe pacemaker.Thisrhythmwasrapidlyreset bybath applicationofc. The oscillations of this endogenous pacemaker time the circadian rhythms of the organism's behavior and physiology

Gillette, Martha U.

310

Sleep, performance, circadian rhythms, and light-dark cycles during two space shuttle flights  

NASA Technical Reports Server (NTRS)

Sleep, circadian rhythm, and neurobehavioral performance measures were obtained in five astronauts before, during, and after 16-day or 10-day space missions. In space, scheduled rest-activity cycles were 20-35 min shorter than 24 h. Light-dark cycles were highly variable on the flight deck, and daytime illuminances in other compartments of the spacecraft were very low (5.0-79.4 lx). In space, the amplitude of the body temperature rhythm was reduced and the circadian rhythm of urinary cortisol appeared misaligned relative to the imposed non-24-h sleep-wake schedule. Neurobehavioral performance decrements were observed. Sleep duration, assessed by questionnaires and actigraphy, was only approximately 6.5 h/day. Subjective sleep quality diminished. Polysomnography revealed more wakefulness and less slow-wave sleep during the final third of sleep episodes. Administration of melatonin (0.3 mg) on alternate nights did not improve sleep. After return to earth, rapid eye movement (REM) sleep was markedly increased. Crewmembers on these flights experienced circadian rhythm disturbances, sleep loss, decrements in neurobehavioral performance, and postflight changes in REM sleep.

Dijk, D. J.; Neri, D. F.; Wyatt, J. K.; Ronda, J. M.; Riel, E.; Ritz-De Cecco, A.; Hughes, R. J.; Elliott, A. R.; Prisk, G. K.; West, J. B.; Czeisler, C. A.

2001-01-01

311

Temperature-independence of circannual variations in circadian rhythms of golden-mantled ground squirrels.  

PubMed

In golden-mantled ground squirrels, phase angles of entrainment of circadian locomotor activity to a fixed light-dark cycle differ markedly between subjective summer and winter. A change in ambient temperature affects entrainment only during subjective winter when it also produces pronounced effects on body temperature (Tb). It was previously proposed that variations in Tb are causally related to the circannual rhythm in circadian entrainment. To test this hypothesis, wheel-running activity and Tb were monitored for 12 to 14 months in castrated male ground squirrels housed in a 14:10 LD photocycle at 21 degrees C. Animals were treated with testosterone implants that eliminated hibernation and prevented the marked winter decline in Tb; these squirrels manifested circannual changes in circadian entrainment indistinguishable from those of untreated animals. Both groups exhibited pronounced changes in phase angle and alpha of circadian wheel-running and Tb rhythms. Seasonal variation in Tb is not necessary for circannual changes in circadian organization of golden-mantled ground squirrels. PMID:10942265

Freeman, D A; Zucker, I

2000-08-01

312

[The interaction of circahoral and circadian rhythms. A cybernetic model].  

PubMed

Parameters of ideal circadian cycle were compared with those of a circadian cycle composed of near-hour fluctuations. The integral cycle was optimized by the algorithm of matrix random search studying the approximation of its parameters to the ideal cycle after the phase shift of the latter. Computer calculations revealed a low efficiency of the search by fluctuation amplitude. The search by phase and frequency was effective in a narrow range of changes and needed time. The average level of fluctuations tuned up practically immediately: ideal and optimized curves coincided in all points. Examples of interactions between day, near-hour and shorter cycles are cited. PMID:1809787

Zaguskin, S L; Grinchenko, S N; Brodski?, V Ia

1991-01-01

313

It is not the parts, but how they interact that determines the behaviour of circadian rhythms across scales and organisms  

PubMed Central

Biological rhythms, generated by feedback loops containing interacting genes, proteins and/or cells, time physiological processes in many organisms. While many of the components of the systems that generate biological rhythms have been identified, much less is known about the details of their interactions. Using examples from the circadian (daily) clock in three organisms, Neurospora, Drosophila and mouse, we show, with mathematical models of varying complexity, how interactions among (i) promoter sites, (ii) proteins forming complexes, and (iii) cells can have a drastic effect on timekeeping. Inspired by the identification of many transcription factors, for example as involved in the Neurospora circadian clock, that can both activate and repress, we show how these multiple actions can cause complex oscillatory patterns in a transcription–translation feedback loop (TTFL). Inspired by the timekeeping complex formed by the NMO–PER–TIM–SGG complex that regulates the negative TTFL in the Drosophila circadian clock, we show how the mechanism of complex formation can determine the prevalence of oscillations in a TTFL. Finally, we note that most mathematical models of intracellular clocks model a single cell, but compare with experimental data from collections of cells. We find that refitting the most detailed model of the mammalian circadian clock, so that the coupling between cells matches experimental data, yields different dynamics and makes an interesting prediction that also matches experimental data: individual cells are bistable, and network coupling removes this bistability and causes the network to be more robust to external perturbations. Taken together, we propose that the interactions between components in biological timekeeping systems are carefully tuned towards proper function. We also show how timekeeping can be controlled by novel mechanisms at different levels of organization. PMID:24904739

DeWoskin, Daniel; Geng, Weihua; Stinchcombe, Adam R.; Forger, Daniel B.

2014-01-01

314

Mind your rhythms: an important role for circadian genes in neuroprotection  

PubMed Central

Circadian rhythms govern nearly every physiological process in our brains and bodies. At the most basic level, the molecular clockwork in each cell interacts with metabolic cycles to influence the redox state, allowing for increased cellular activity at specific times of day. In this issue of the JCI, Musiek et al. show that genetic disruptions in the positive arm of the molecular clock can lead to severe astrogliosis, which likely occurs through disruptions in output genes that keep oxidative stress in check. This study demonstrates the importance of proper circadian protein function in the maintenance of neuronal integrity. PMID:24270412

McClung, Colleen A.

2013-01-01

315

The suprachiasmatic nucleus is essential for circadian body temperature rhythms in hibernating ground squirrels.  

PubMed

Body temperature (T(b)) was recorded at 10 min intervals over 2.5 years in female golden-mantled ground squirrels that sustained complete ablation of the suprachiasmatic nucleus (SCNx). Animals housed at an ambient temperature (T(a)) of 6.5 degrees C were housed in a 12 hr light/dark cycle for 19 months followed by 11 months in constant light. The circadian rhythm of T(b) was permanently eliminated in euthermic and torpid SCNx squirrels, but not in those with partial destruction of the SCN or in neurologically intact control animals. Among control animals, some low-amplitude T(b) rhythms during torpor were driven by small (<0.1 degrees C) diurnal changes in T(a). During torpor bouts in which T(b) rhythms were unaffected by T(a), T(b) rhythm period ranged from 23.7 to 28.5 hr. Both SCNx and control squirrels were more likely to enter torpor at night and to arouse during the day in the presence of the light/dark cycle, whereas entry into and arousal from torpor occurred at random clock times in both SCNx and control animals housed in constant light. Absence of circadian rhythms 2.5 years after SCN ablation indicates that extra-SCN pacemakers are unable to mediate circadian organization in euthermic or torpid ground squirrels. The presence of diurnal rhythms of entry into and arousal from torpor in SCNx animals held under a light/dark cycle, and their absence in constant light, suggest that light can reach the retina of hibernating ground squirrels maintained in the laboratory and affect hibernation via an SCN-independent mechanism. PMID:11756519

Ruby, Norman F; Dark, John; Burns, D Erik; Heller, H Craig; Zucker, Irving

2002-01-01

316

Free-running circadian rhythms of muscle strength, reaction time, and body temperature in totally blind people.  

PubMed

Light is the major synchronizer of circadian rhythms. In the absence of light, as for totally blind people, some variables, such as body temperature, have an endogenous period that is longer than 24 h and tend to be free running. However, the circadian rhythm of muscle strength and reaction time in totally blind people has not been defined in the literature. The objective of this study was to determine the period of the endogenous circadian rhythm of the isometric and isokinetic contraction strength and simple reaction time of totally blind people. The study included six totally blind people with free-running circadian rhythms and four sighted people (control group). Although the control group required only a single session to determine the circadian rhythm, the blind people required three sessions to determine the endogenous period. In each session, isometric strength, isokinetic strength, reaction time, and body temperature were collected six different times a day with an interval of at least 8 h. The control group had better performance for strength and reaction time in the afternoon. For the blind, this performance became delayed throughout the day. Therefore, we conclude that the circadian rhythms of strength and simple reaction time of totally blind people are within their free-running periods. For some professionals, like the blind paralympic athletes, activities that require large physiological capacities in which the maximum stimulus should match the ideal time of competition may result in the blind athletes falling short of their expected performance under this free-running condition. PMID:22618303

Squarcini, Camila Fabiana Rossi; Pires, Maria Laura Nogueira; Lopes, Cleide; Benedito-Silva, Ana Amélia; Esteves, Andrea Maculano; Cornelissen-Guillaume, Germaine; Matarazzo, Carolina; Garcia, Danilo; da Silva, Maria Stella Peccin; Tufik, Sergio; de Mello, Marco Túlio

2013-01-01

317

Brief Communication Circadian Rhythm Generation and Entrainment  

E-print Network

secretion in the absence of external cues. Several other tissues, including the retina, olfactory bulb of primary astrocyte cultures. Wild-type and transgenic rats (Japanese Wistar; a generous gift from Dr. H cultures of cortical astrocytes from Period2::luciferase (Per2::luc) knock-in mice and Period1::luciferase

Newman, Eric A.

318

Circadian Rhythms in Cognitive Processes: Implications for School Learning  

ERIC Educational Resources Information Center

Circadian variations have been found in cognitive processes, such as attention, working memory, and executive functions, which may explain oscillations in the performance of many tasks. These cognitive processes improve during the day and decrease during the night and early hours of the morning. Sleep deprivation further decreases these cognitive…

Valdez, Pablo; Ramírez, Candelaria; García, Aída

2014-01-01

319

Circadian rhythm and sudden death in heart failure  

Microsoft Academic Search

OBJECTIVEThe purpose of this study was to address the timing of sudden death in advanced heart failure patients.BACKGROUNDSudden death is a catastrophic event in cardiovascular disease. It has a circadian pattern prominent in the early am, which has been thought to be due to a surge of sympathetic stimulation. We postulated that the distribution of events in advanced heart failure,

Peter A Carson; Christopher M O’Connor; Alan B Miller; Susan Anderson; Robert Belkin; Gerald W Neuberg; John H Wertheimer; David Frid; Anne Cropp; Milton Packer

2000-01-01

320

Counting circadian cycles to determine the period of a circasemilunar rhythm in a marine insect.  

PubMed

Semilunar and lunar rhythms are often controlled endogenously, but the mechanisms of their respective free-run periods, when external factors are absent, are mostly unclear. In this investigation, the authors studied the mechanism controlling the period of the circasemilunar emergence rhythm of a marine midge, Pontomyia oceana, in southern Taiwan. Experimental approaches were adopted with various artificial light-dark (LD) periods, or T, from 22 to 28?h per cycle in the first experiment, and 18 to 30?h per cycle in the second experiment, as treatments on the same cohorts of midge larvae. The responses in emergence days were directly proportional to the magnitude of the treatments, just as that predicted by the frequency demultiplication hypothesis. A counting mechanism is thus the only hypothesis supported by this finding. To further test whether it is endogenous oscillations that are counted, submultiples as well as multiples of 24?h, i.e., 6, 12, 24, and 48?h per cycle, were used as T. The midges under all these treatments emerged at similar days. This result supports the hypothesis that endogenous circadian oscillations, not external LD cycles, are counted in this circasemilunar emergence rhythm of the marine midge. This paper reports a first case supporting the frequency demultiplication hypothesis in a circasemilunar rhythm that is based on counting the cycles of endogenous circadian rhythms. PMID:23130850

Soong, Keryea; Chang, Yin-Hao

2012-12-01

321

Circadian rhythm of histamine metabolism in the rabbit central nervous system (CNS): Analysis of brain and ocular structures  

Microsoft Academic Search

The circadian rhythm of the level of histamine (HI) and histidine decarboxylase (HD) and histamine-methyltransferase (HMT) activity in 6 brain and 5 ocular structures of the rabbit was studied. Clear circadian variations of the histaminergic parameters in two brain (hypothalamus and lateral geniculate body) and two ocular (retina and iris-ciliary body) tissues were found. It is suggested that HI in

J. Z. Nowak; R. Socko; P. Uznanski

1988-01-01

322

The influence of circadian rhythms on pre- and post-prandial metabolism in the snake Lamprophis fuliginosus  

Microsoft Academic Search

Measuring standard metabolic rate (SMR) and specific dynamic action (SDA) has yielded insight into patterns of energy expenditure in snakes, but less emphasis has been placed on identifying metabolic variation and associated energy cost of circadian rhythms. To estimate SMR, SDA, and identify metabolic variation associated with circadian cycles in nocturnally active African house snakes (Lamprophis fuliginosus), we measured oxygen

J. H. Roe; W. A. Hopkins; J. W. Snodgrass; J. D. Congdon

2004-01-01

323

The influence of circadian rhythms on pre- and post-prandial metabolism in the snake Lamprophis fuliginosus  

Microsoft Academic Search

Abstract Measuring standard metabolic rate (SMR) and specific dynamic,action (SDA) has yielded insight into patterns of energy expenditure in snakes, but less emphasis has been placed on identifying metabolic variation and associated energy cost of circadian rhythms. To estimate SMR, SDA, and identify metabolic variation associated with circadian cycles in nocturnally active African house snakes (Lamprophis fuliginosus), we measured oxygen

J. h. Roe; ; W. A. Hopkins; J. w. Snodgrass; J. d. Congdon

324

CRY, a Drosophila Clock and Light-Regulated Cryptochrome, Is a Major Contributor to Circadian Rhythm Resetting and Photosensitivity  

Microsoft Academic Search

Light is a major environmental signal for circadian rhythms. We have identified and analyzed cry, a novel Drosophila cryptochrome gene. All characterized family members are directly photosensitive and include plant blue light photoreceptors. We show that cry transcription is under circadian regulation, influenced by the Drosophila clock genes period, timeless, Clock, and cycle. We also show that cry protein levels

Patrick Emery; W. Venus So; Maki Kaneko; Jeffrey C Hall; Michael Rosbash

1998-01-01

325

[New hypnotics ramelteon for the treatment of insomniacs with circadian rhythm disturbance].  

PubMed

Ramelteon is a new class of sleep agent that selectively binds to the melatonin type 1 (MT1) and type 2 (MT2) receptors in the suprachiasmatic nucleus (SCN), instead of binding to GABA-A receptors such as with traditional hypnotics benzodiazepines. Ramelteon exhibits not only acute sleep-promoting effect but also circadian phase-shifting effect via MT1 and MT2 receptors respectively, and has been revealed to contribute to the treatment of acute and chronic insomnia in patients with circadian rhythm sleep disorders(sleep-wake rhythm disorders) or with inappropriate timing of sleep habits. Optimal administration plan for insomniac patients to induce these characteristic sleep-modulating effects by ramelteon was discussed. PMID:22690618

Mishima, Kazuo

2012-06-01

326

Adipose circadian rhythms: translating cellular and animal studies to human physiology.  

PubMed

Emerging links between circadian rhythms and metabolism promise much for the understanding of metabolic physiology and pathophysiology, in which white adipose tissue (WAT) plays a prominent role. Many WAT endocrine molecules, termed adipokines, display rhythmic plasma concentration. Moreover, similar to most other tissues, WAT exhibits widespread 24-h variation in gene expression, with approximately 20% of the murine adipose transcriptome estimated to undergo daily variation. A major limitation to human chronobiology research is the availability of physiologically defined peripheral tissues. To date most analyses of in vivo human peripheral clocks has been limited to blood leucocytes. However, subcutaneous adipose tissue represents a novel opportunity to study peripheral molecular rhythms that are of clearly defined metabolic relevance. This review summarises basic concepts of circadian and metabolic physiology before then comparing alternative protocols used to analyse the rhythmic properties of human adipose tissue. PMID:21664232

Johnston, Jonathan D

2012-02-01

327

Disrupted reproduction, estrous cycle, and circadian rhythms in female vasoactive intestinal peptide deficient mice  

PubMed Central

The female reproductive cycle is gated by the circadian timing system and may be vulnerable to disruptions in the circadian system. Prior work suggests that vasoactive intestinal peptide (VIP) expressing neurons in the suprachiasmatic nucleus (SCN) are one pathway by which the circadian clock can influence the estrous cycle but the impact of the loss of this peptide on reproduction has not been assessed. In the present study, we first examine the impact of the genetic loss of the neuropeptide VIP on the reproductive success of female mice. Significantly, mutant females produced about half the offspring of their wild type sisters even when mated to the same males. We also find that VIP-deficient females exhibit a disrupted estrous cycle i.e. ovulation occurs less frequently and results in the release of fewer oocytes compared to controls. Circadian rhythms of wheel running activity are disrupted in the female mutant mice as are the spontaneous electrical activity of dorsal SCN neurons. On a molecular level, the VIP-deficient SCN tissue exhibit lower amplitude oscillations with altered phase relationships between the SCN and peripheral oscillators as measured by PER2-driven bioluminescence. The simplest explanation of our data is that the loss of VIP results in a weakened SCN oscillator which reduces the synchronization of the female circadian system. These results clarify one of the mechanisms by which disruption of the circadian system reduces female reproductive success. PMID:25252712

Loh, Dawn Hsiao-Wei; Kuljis, Dika Ana; Azuma, Lauren; Wu, Yingfei; Truong, Danny; Wang, Huei-Bin; Colwell, Christopher Scott

2015-01-01

328

A statistical model of the human core-temperature circadian rhythm  

NASA Technical Reports Server (NTRS)

We formulate a statistical model of the human core-temperature circadian rhythm in which the circadian signal is modeled as a van der Pol oscillator, the thermoregulatory response is represented as a first-order autoregressive process, and the evoked effect of activity is modeled with a function specific for each circadian protocol. The new model directly links differential equation-based simulation models and harmonic regression analysis methods and permits statistical analysis of both static and dynamical properties of the circadian pacemaker from experimental data. We estimate the model parameters by using numerically efficient maximum likelihood algorithms and analyze human core-temperature data from forced desynchrony, free-run, and constant-routine protocols. By representing explicitly the dynamical effects of ambient light input to the human circadian pacemaker, the new model can estimate with high precision the correct intrinsic period of this oscillator ( approximately 24 h) from both free-run and forced desynchrony studies. Although the van der Pol model approximates well the dynamical features of the circadian pacemaker, the optimal dynamical model of the human biological clock may have a harmonic structure different from that of the van der Pol oscillator.

Brown, E. N.; Choe, Y.; Luithardt, H.; Czeisler, C. A.

2000-01-01

329

Assessing circadian rhythms in propofol PK and PD during prolonged infusion in ICU patients  

Microsoft Academic Search

This study evaluates possible circadian rhythms during prolonged propofol infusion in patients in the intensive care unit.\\u000a Eleven patients were sedated with a constant propofol infusion. The blood samples for the propofol assay were collected every\\u000a hour during the second day, the third day, and after the termination of the propofol infusion. Values of electroencephalographic\\u000a bispectral index (BIS), arterial blood

Agnieszka Bienert; Krzysztof Kusza; Katarzyna Wawrzyniak; Edmund Grze?kowiak; Zenon J. Kokot; Jan Matysiak; Tomasz Grabowski; Anna Wolc; Pawe? Wiczling; Mi?osz Regulski

2010-01-01

330

Jet lag, circadian rhythm sleep disturbances, and depression: the role of melatonin and its analogs  

Microsoft Academic Search

Traveling through several time zones results in a constellation of symptoms known as jet lag. These include reduced alertness,\\u000a daytime fatigue, loss of appetite, reduced cognitive skills, and disruption of the sleep\\/wake cycle. In susceptible air travel\\u000a passengers, jet lag may exacerbate affective illness and result in psychiatric morbidity. Dysregulation of circadian rhythms\\u000a and melatonin secretion represent the common underlying

Venkatramanujam Srinivasan; Jarnail Singh; Seithikurippu R. Pandi-Perumal; Gregory M. Brown; David Warren Spence; Daniel P. Cardinali

2010-01-01

331

Lifelines Episode 16: Circadian Rhythm and Jet Lag; Exercise and Appetite  

NSDL National Science Digital Library

This is a free audio podcast from the American Physiological Society. Discussion questions, related research, and other teaching resources are available by clicking the "collection" tab in the left hand column. Interviews with Clifford Saper on circadian rhythm and jet lag (begins at 3:14) and David J. Stensel on exercise and appetite (begins at 11:54). Click here for the full study by David Stensel. The Buzz in Physiology (Begins at 1:25) Total Time: 20:27

APS Communications Office (American Physiological Society Communications Office)

2008-12-01

332

The Downs and Ups of Mechanistic Research: Circadian Rhythm Research as an Exemplar  

Microsoft Academic Search

In the context of mechanistic explanation, reductionistic research pursues a decomposition of complex systems into their component\\u000a parts and operations. Using research on the mechanisms responsible for circadian rhythms, I consider both the gains that have\\u000a been made by discovering genes and proteins that figure in these intracellular oscillators and also highlight the increasingly\\u000a recognized need to understand higher-level integration,

William Bechtel

2010-01-01

333

Phase-shifting human circadian rhythms: influence of sleep timing, social contact and light exposure  

NASA Technical Reports Server (NTRS)

1. Both the timing of behavioural events (activity, sleep and social interactions) and the environmental light-dark cycle have been reported to contribute to entrainment of human circadian rhythms to the 24 h day. Yet, the relative contribution of those putative behavioural synchronizers to that of light exposure remains unclear. 2. To investigate this, we inverted the schedule of rest, sedentary activity and social contact of thirty-two young men either with or without exposure to bright light. 3. On this inverted schedule, the endogenous component of the core temperature rhythm of subjects who were exposed to bright light showed a significant phase shift, demonstrating that they were adapting to the new schedule. In contrast, the core temperature rhythm of subjects who were not exposed to bright light moved on average 0.2 h later per day and after 10 days had not significantly adapted to the new schedule. 4. The direction of phase shift in the groups exposed to bright light was dependent on the time of bright light exposure, while control subjects drifted to a later hour regardless of the timing of their schedule of sleep timing, social contact and meals. 5. These results support the concept that the light-dark cycle is the most important synchronizer of the human circadian system. They suggest that inversion of the sleep-wake, rest-activity and social contact cycles provides relatively minimal drive for resetting the human circadian pacemaker. 6. These data indicate that interventions designed to phase shift human circadian rhythms for adjustment to time zone changes or altered work schedules should focus on properly timed light exposure.

Duffy, J. F.; Kronauer, R. E.; Czeisler, C. A.

1996-01-01

334

Circadian rhythm disorder in a rare disease: Smith–Magenis syndrome  

Microsoft Academic Search

Smith–Magenis syndrome (SMS) is a clinically recognizable contiguous gene syndrome, caused by interstitial deletion of chromosome 17p11.2. The SMS phenotype include distinctive facial features, developmental delay and neurobehavioral abnormalities. The patients present major sleep disturbances ascribed to a phase shift of their circadian rhythm of melatonin with a paradoxical diurnal secretion of the hormone. Treatment with morning beta-blockers and evening

Hélène De Leersnyder; Bruno Claustrat; Arnold Munnich; Alain Verloes

2006-01-01

335

Toward a classification of medications for sleep and circadian rhythm disorders  

PubMed Central

While some systems classify medications according to therapeutic class, others are based on the mechanism of action of the drugs. The two main classifications of medications used to treat patients in the United States are those of the United States Pharmacopeia and US Food and Drug Administration, and they vary in their organization of the medication categories. Here we propose a taxonomy for medications used to treat sleep and circadian rhythm disorders based on symptoms and disorders. PMID:24363563

Thorpy, Michael J; Roth, Thomas

2013-01-01

336

Melatonin sleep and circadian rhythms: rationale for development of specific melatonin agonists  

Microsoft Academic Search

Abstract Circadian rhythm sleep disorders (CRSDs), whether chronic or transient, affect a broad range of individuals, including many elderly, those with severe visual impairments, shift workers, and jet travelers moving rapidly across many time zones. In addition, various forms of insomnia affect another large sector of the population. A feature common,among,CRSDs and some,forms of insomnia,is sensitivity to the hormone melatonin,

Fred W. Turek; Martha U. Gillette

337

Daily Melatonin Treatments Regulate the Circadian Melatonin Rhythm in the Adult Djungarian Hamster  

Microsoft Academic Search

The present study tested the hypothesis that daily melatonin treatments influence the biological clock mechanism controlling the circadian melatonin rhythm. Adult male and female Djungarian hamsters in light:dark = 16L:8D (lights on 0300-1900 h) were administered melatonin subcutaneously (s.c.) each day (5 ?g\\/0.2 ml saline) in the morning at 1000 h (AM) or late afternoon at 1700 h (PM); controls

Steven M. Yellon

1996-01-01

338

Assessing circadian rhythms in propofol PK and PD during prolonged infusion in ICU patients.  

PubMed

This study evaluates possible circadian rhythms during prolonged propofol infusion in patients in the intensive care unit. Eleven patients were sedated with a constant propofol infusion. The blood samples for the propofol assay were collected every hour during the second day, the third day, and after the termination of the propofol infusion. Values of electroencephalographic bispectral index (BIS), arterial blood pressure, heart rate, blood oxygen saturation and body temperature were recorded every hour at the blood collection time points. A two-compartment model was used to describe propofol pharmacokinetics. Typical values of the central and peripheral volume of distribution and inter-compartmental clearance were V(C) = 27.7 l, V(T) = 801 l, and CL(D) = 2.73 l/min. The systolic blood pressure (SBP) was found to influence the propofol metabolic clearance according to Cl (l/min) = 2.65 x (1-0.00714 x (SBP-135)). There was no significant circadian rhythm detected with respect to propofol pharmacokinetics. The BIS score was assessed as a direct effect model with EC(50) equal 1.98 mg/l. There was no significant circadian rhythm detected within the BIS scores. We concluded that the light-dark cycle did not influence propofol pharmacokinetics and pharmacodynamics in intensive care units patients. The lack of night-day differences was also noted for systolic blood pressure, diastolic blood pressure and blood oxygenation. Circadian rhythms were detected for heart rate and body temperature, however they were severely disturbed from the pattern of healthy patients. PMID:20544262

Bienert, Agnieszka; Kusza, Krzysztof; Wawrzyniak, Katarzyna; Grze?kowiak, Edmund; Kokot, Zenon J; Matysiak, Jan; Grabowski, Tomasz; Wolc, Anna; Wiczling, Pawe?; Regulski, Mi?osz

2010-06-01

339

Involvement of 5-HT? receptors in vortioxetine's modulation of circadian rhythms and episodic memory in rodents.  

PubMed

Since poor circadian synchrony and cognitive dysfunction have been linked to affective disorders, antidepressants that target key 5-HT (serotonin) receptor subtypes involved in circadian rhythm and cognitive regulation may have therapeutic utility. Vortioxetine is a multimodal antidepressant that inhibits 5-HT1D, 5-HT3, 5-HT7 receptor activity, 5-HT reuptake, and enhances the activity of 5-HT1A and 5-HT1B receptors. In this study, we investigated the effects of vortioxetine on the period length of PER2::LUC expression, circadian behavior, and episodic memory, using tissue explants from genetically modified PER2::LUC mice, locomotor activity rhythm monitoring, and the object recognition test, respectively. Incubation of tissue explants from the suprachiasmatic nucleus of PER2::LUC mice with 0.1 ?M vortioxetine increased the period length of PER2 bioluminescence. Monitoring of daily wheel-running activity of Sprague-Dawley rats treated with vortioxetine (10 mg/kg, s.c.), alone or in combination with the 5-HT1A receptor agonist flesinoxan (2.5 mg/kg, s.c.) or the 5-HT7 receptor antagonist SB269970 (30 mg/kg, s.c.), just prior to activity onset revealed significant delays in wheel-running behavior. The increase in circadian period length and the phase delay produced by vortioxetine were abolished in the presence of the 5-HT7 receptor partial agonist AS19. Finally, in the object recognition test, vortioxetine (10 mg/kg, i.p.) increased the time spent exploring the novel object during the retention test and this effect was prevented by AS19 (5 mg/kg, i.p.). In conclusion, the present study shows that vortioxetine, partly via its 5-HT7 receptor antagonism, induced a significant effect on circadian rhythm and presented promnesic properties in rodents. PMID:25446573

Westrich, Ligia; Haddjeri, Nasser; Dkhissi-Benyahya, Ouria; Sánchez, Connie

2015-02-01

340

Effects of microgravity on circadian rhythms in insects  

NASA Technical Reports Server (NTRS)

The desert beetle Trigonoscelis gigas Reitt. was used as a biological model in studies that examined the effects of space flight on the circadian timing system. Results from studies aboard the Bion-10, Bion-11, and Photon-11 missions are reported. The control study is an ongoing Mir experiment. The studies indicate that the free-running period in beetles may be longer during space flight.

Alpatov, A. M.; Hoban-Higgins, T. M.; Fuller, C. A.; Lazarev, A. O.; Rietveld, W. J.; Tschernyshev, V. B.; Tumurova, E. G.; Wassmer, G.; Zotov, V. A.

1998-01-01

341

A time to think: Circadian rhythms in human cognition  

Microsoft Academic Search

Although peaks and troughs in cognitive performance characterize our daily functioning, time-of-day fluctuations remain marginally considered in the domain of cognitive psychology and neuropsychology. Here, we attempt to summarize studies looking at the effects of sleep pressure, circadian variations, and chronotype on cognitive functioning in healthy subjects. The picture that emerges from this assessment is that beyond physiological variables, time-of-day

Christina Schmidt; Fabienne Collette; Christian Cajochen; Philippe Peigneux

2007-01-01

342

Sleep and circadian rhythms in long duration space flight - Antarctica as an analogue environment  

NASA Technical Reports Server (NTRS)

The feasibility of using Antarctica as an environment for studying the impact of unusual 24 h environmental cycles (zeitgebers) on the circadian system is discussed. Adaptation of circadian rhythms and sleep of three scientists travelling from New Zealand to Antarctica during summer (which is analogous to arrival at a lunar base during the lunar day) has been studied. Data obtained indicate that sleep occurred at the same clock time, but sleep quality was poorer in Antarctica, which can be explained by the fact that the circadian system delayed by about 2 h in Antarctica, as would be expected in a weaker zeitgeber environment. It is suggested that sleep could be improved by altering patterns of exposure to the available zeitgebers to increase their effective strength.

Gander, Philippa H.

1992-01-01

343

The development and course of bipolar spectrum disorders: an integrated reward and circadian rhythm dysregulation model.  

PubMed

In this article, we present and review the evidence for two major biopsychosocial theories of the onset and course of bipolar spectrum disorders (BSDs) that integrate behavioral, environmental, and neurobiological mechanisms: the reward hypersensitivity and the social/circadian rhythm disruption models. We describe the clinical features, spectrum, age of onset, and course of BSDs. We then discuss research designs relevant to demonstrating whether a hypothesized mechanism represents a correlate, vulnerability, or predictor of the course of BSDs, as well as important methodological issues. We next present the reward hypersensitivity model of BSD, followed by the social/circadian rhythm disruption model of BSD. For each model, we review evidence regarding whether the proposed underlying mechanism is associated with BSDs, provides vulnerability to the onset of BSDs, and predicts the course of BSDs. We then present a new integrated reward/circadian rhythm (RCR) dysregulation model of BSD and discuss how the RCR model explains the symptoms, onset, and course of BSDs. We end with recommendations for future research directions. PMID:25581235

Alloy, Lauren B; Nusslock, Robin; Boland, Elaine M

2015-03-28

344

Eyeless Mexican Cavefish Save Energy by Eliminating the Circadian Rhythm in Metabolism  

PubMed Central

The eyed surface form and eyeless cave form of the Mexican tetra Astyanax mexicanus experience stark differences in the daily periodicities of light, food and predation, factors which are likely to have a profound influence on metabolism. We measured the metabolic rate of Pachón cave and surface fish at a fixed swimming speed under light/dark and constant dark photoperiods. In constant darkness surface forms exhibited a circadian rhythm in metabolism with an increase in oxygen demand during the subjective daytime, whereas cave forms did not. The lack of circadian rhythm in metabolism leads to a 27% energy savings for Pachón cave fish compared to surface fish when comparing both forms in their natural photoperiods. When surface forms were tested under constant dark conditions they expended 38% more energy than cave forms under equivalent conditions. Elimination of the circadian rhythm in metabolism may be a general feature of animals that live in perpetually dark food-limited environments such as caves or the deep sea. PMID:25251018

Moran, Damian; Softley, Rowan; Warrant, Eric J.

2014-01-01

345

The Development and Course of Bipolar Spectrum Disorders: An Integrated Reward and Circadian Rhythm Dysregulation Model  

PubMed Central

In this article, we present and review the evidence for two major biopsychosocial theories of the onset and course of bipolar spectrum disorders (BSDs) that integrate behavioral, environmental, and neurobiological mechanisms: the reward hypersensitivity and the social and circadian rhythm disruption models. We describe the clinical features, spectrum, age of onset, and course of BSDs. We then discuss research designs relevant to demonstrating whether a hypothesized mechanism represents a correlate, vulnerability, or predictor of the course of BSDs, as well as important methodological issues. We next present the reward hypersensitivity model of BSD, followed by the social/circadian rhythm disruption model of BSD. For each model, we review evidence regarding whether the proposed underlying mechanism is associated with BSDs, provides vulnerability to the onset of BSDs, and predicts the course of BSDs. We then present a new integrated reward/circadian rhythm (RCR) dysregulation model of BSD and discuss how the RCR model explains the symptoms, onset, and course of BSDs. We end with recommendations for future research directions. PMID:25581235

Alloy, Lauren B.; Nusslock, Robin; Boland, Elaine M.

2014-01-01

346

Demonstration of Circadian Rhythm in Heart Rate Turbulence using Novel Application of Correlator Functions  

E-print Network

Background: It has been difficult to demonstrate circadian rhythm in the two parameters of heart rate turbulence, turbulence onset (TO) and turbulence slope (TS). Objective: To devise a new method for detecting circadian rhythm in noisy data, and apply it to selected Holter recordings from two post-myocardial infarction databases, Cardiac Arrhythmia Suppression Trial (CAST, n=684) and Innovative Stratification of Arrhythmic Risk (ISAR, n=327). Methods: For each patient, TS and TO were calculated for each hour with >4 VPCs. An autocorrelation function Corr(Delta t) = was then calculated, and averaged over all patients. Positive Corr(Delta t) indicates that TS at a given hour and Delta t hours later are similar. TO was treated likewise. Simulations and mathematical analysis showed that circadian rhythm required Corr(Delta t) to have a U-shape consisting of positive values near Delta t=0 and 23, and negative values for intermediate Delta t. Significant deviation of Corr(Delta t) from the correlator function of ...

Watanabe, M; Barthel, P; Bauer, A; Schmidt, G; Schneider, R; Stein, P; Alford, Mark; Barthel, Petra; Bauer, Axel; Schmidt, Georg; Schneider, Raphael; Stein, Phyllis; Watanabe, Mari

2006-01-01

347

[Effects of ramelteon on a patient with circadian rhythm sleep disorder and mood disorder].  

PubMed

Ramelteon is a novel hypnotic characterized by its action as a melatonin receptor (MT1/MT2) agonist. It has been reported that ramelteon can alter the phase of the sleep period. We report a patient with circadian rhythm sleep disorder and mood disorder who improved with ramelteon. A 25-year-old man had a 5-year history of emotional instability, excessive daytime sleepiness, and difficulty awakening. He had been diagnosed with mood disorder and narcolepsy by a psychiatrist. Sertraline, milnacipran, valproate, and methylphenidate were ineffective, and so he presented to our hospital. Interview data and a sleep log demonstrated a delayed sleep phase. As other examinations such as actigraphy and video-polysomnography indicated no other diseases, the patient was diagnosed with circadian rhythm sleep disorder, delayed sleep phase type (ICSD-2). In addition, his mental symptoms were consistent with the criteria for cyclothymia (ICD-10). After the administration of ramelteon, the phase of his sleep period gradually advanced and his emotional instability improved. Because of the high rate of comorbidity between these two diseases, we should be aware of circadian rhythm sleep disorders that are masked by mood disorders. PMID:25711117

Yoshihara, Shinsuke; Yoshizawa, Mondo; Shirata, Ayaka; Matsuda, Mika; Tamashiro, Motoyuki; Saito, Ichiro; Sakamoto, Kazutaka; Fujimura, Youta; Tamura, Yoshiyuki; Chiba, Shigeru

2014-01-01

348

Light as a central modulator of circadian rhythms, sleep and affect  

PubMed Central

Light has profoundly influenced the evolution of life on earth. As widely appreciated, light allows us to generate images of our environment. However, light, through the atypical intrinsically photosensitive retinal ganglion cells (ipRGCs; Box 1), also influences behaviors that are essential for our health and quality of life, yet are independent of image formation. These include the synchronization of the circadian clock to the solar day, tracking of seasonal changes, and regulation of sleep. Irregular light environments lead to problems in circadian rhythms and sleep, which eventually cause mood and learning deficits. Recently, it was found that irregular light can also directly impact mood and learning without producing major disruptions in circadian rhythms and sleep. Here, we will discuss the indirect and direct influence of light on mood and learning and provide a model for how light, the circadian clock, and sleep interact to influence mood and cognitive functions. Box 1Intrinsically photosensitive retinal ganglion cells (ipRGCs)Retinal photoreceptors transduce light energy into electrical signals that initiate vision. The classical photoreceptors, rods and cones, possess modified cilia that consist of stacks of membranes in which photopigments (rhodopsin and cone opsins) are concentrated. Rods are exquisitely sensitive and are able to detect even a few photons. Rods are therefore used for night vision. Cones are less sensitive than rods and are used for day and color vision. Color vision is mediated by cone photoreceptors that express cone-opsins with sensitivity peaks at different wavelengths (colors) of light. Humans have three cone types: short, mid and long wavelength sensitive cones (for simplicity, we will refer to these as blue, green and red cones, respectively). Rods and cones relay photic information through multisynaptic pathways to retinal ganglion cells (RGCs), which innervate different areas in the brain for complex visual processing13.A surprising discovery showed that a subpopulation of RGCs is intrinsically photosensitive and express the photopigment melanopsin. These cells were thus termed ipRGCs17–19. The melanopsin gene (Opn4) was originally cloned from Xenopus laevis dermal melanophores, and was shown to have orthologs in many mammalian species, including humans141. Sequence analysis shows that melanopsin shares more homology with invertebrate opsins than with vertebrate opsins, suggesting that melanopsin may use a different mechanism for light signaling than that used by the photopigments present in the rods and cones of vertebrates142. ipRGCs do not have modified membranes in which the photopigment can be concentrated: thus, melanopsin protein is expressed uniformly throughout the soma, dendrites, and the initial segment of the axon143. The lack of membrane specialization makes ipRGCs less sensitive to light than rods and cones. However, ipRGCs are able to incorporate light signals over extended period of time, resulting in an increase in their sensitivity during prolonged light stimulation. ipRGCs are most sensitive to wavelengths of light that are in the blue region of the light spectrum144, 145. As ganglion cells, ipRGCs also convey light information from rods and cones in addition to their intrinsic melanopsin-dependent pathway and can control a variety of light-mediated behaviors30.Originally, ipRGCs were thought to comprise a uniform population, however, recent discoveries revealed that ipRGCs are highly diverse, comprising at least five distinct subtypes (M1-M5) in rodents based on morphological and electrophysiological analyses22–29. The originally identified population is now known as M1 ipRGCs and project predominantly to brain regions involved in non-image forming visual functions, whereas the non-M1 ipRGCs show widespread projections to areas in the brain important for image formation. ipRGC subtypes express varying levels of the melanopsin protein and have different patterns of dendrite stratification in the inner plexiform layer (IPL)27, 28, 146, 147, indicating

LeGates, T.A.; Fernandez, D.C.; Hattar, S

2014-01-01

349

Circadian Rhythms in the Suprachiasmatic Nucleus are Temperature-Compensated and Phase-Shifted by Heat Pulses In Vitro  

Microsoft Academic Search

Temperature compensation and the effects of heat pulses on rhythm phase were assessed in the suprachiasmatic nucleus (SCN). Circadian neuronal rhythms were recorded from the rat SCN at 37 and 31°C in vitro. Rhythm period was 23.9 6 0.1 and 23.7 6 0.1 hr at 37 and 31°C, respectively; the Q10 for tau was 0.99. Heat pulses were administered at

Norman F. Ruby; D. Erik Burns; H. Craig Heller

1999-01-01

350

Pinealectomy shortens resynchronisation times of house sparrow ( Passer domesticus) circadian rhythms  

NASA Astrophysics Data System (ADS)

In many birds periodic melatonin secretion by the pineal organ is essential for the high-amplitude self-sustained output of the circadian pacemaker, and thus for the persistence of rhythmicity in 24 h oscillations controlled by it. The elimination of the pineal melatonin rhythm, or a reduction of its amplitude, renders the circadian pacemaker a less self-sustained, often highly damped, oscillatory system. A reduction in the degree of self-sustainment of a rhythm should not only increase its range of entrainment but also shorten the resynchronization times following phase-shifts of the zeitgeber. This hypothesis has not yet been directly tested. We therefore carried out the present study in which house sparrows (Passer domesticus) were subjected to both 6-h advance and 6-h delay phase-shifts of the light-dark cycle before and after the pinealectomy, and the rhythms in locomotion and feeding were recorded. The results indicate that following the delay, but not the advance, phase shift, resynchronization times were significantly shorter after pinealectomy. The dependence of resynchronization times on the presence or absence of the pineal organ is not only of theoretical interest but might also be of functional significance in the natural life of birds. A reduction or elimination of the amplitude of the melatonin secretion rhythm by the pineal organ might be responsible for faster adjustment to changes in zeitgeber conditions in nature.

Kumar, Vinod; Gwinner, Eberhard

2005-09-01

351

Masking of the circadian rhythms of heart rate and core temperature by the rest-activity cycle in man  

NASA Technical Reports Server (NTRS)

Experiments were conducted to estimate the magnitude of the masking effect produced in humans by alternate periods of physical activity and rest or sleep on the circadian rhythms of heart rate and core temperature. The heart rate, rectal temperature, and nondominant wrist activity were monitored in 12 male subjects during 6 days of normal routine at home and during 6 days of controlled bed-rest regimen. The comparisons of averaged waveforms for the activity, heart rate, and temperature indicated that about 45 percent of the range of the circadian heart rate rhythm during normal routine and about 14 percent of the range of the circadian temperature rhythm were attributable to the effects of activity. The smaller effect of activity on the temperature rhythm may be partially attributable to the fact that core temperature is being more rigorously conserved than heart rate, at least during moderate exercise.

Gander, Philippa H.; Connell, Linda J.; Graeber, R. Curtis

1986-01-01

352

Hypoxia disrupts the expression levels of circadian rhythm genes in hepatocellular carcinoma.  

PubMed

Disturbance in the expression of circadian rhythm genes is a common feature in certain types of cancer, however the mechanisms mediating this disturbance remain to be elucidated. The present study aimed to investigate the effect of hypoxia on the expression of circadian rhythm genes in liver cancer cells and to identify the mechanisms underlying this effect in hepatocellular carcinoma (HCC). The HCC cell line, PLC/PRF/5. was treated with either a vehicle control or CoCl2 at 50, 100 or 200 µ? for 24 h. Following treatment, the protein expression levels of hypoxia?inducible factor (HIF)?1? and HIF?2? were detected by western blotting and the mRNA expression levels of circadian rhythm genes, including circadian locomotor output cycles kaput (Clock), brain and muscle Arnt?like 1 (Bmal1), period (Per)1, Per2, Per3, cryptochrome (Cry)1, Cry2 and casein kinase I? (CKI?), were detected by reverse transcription quantitative polymerase chain reaction (RT?qPCR). Expression plasmids containing HIF?1? or HIF?2? were transfected into the PLC/PRF/5 cells using liposomes and RT?qPCR was used to determine the effects of the transfections on the expression levels of circadian rhythm genes. Following treatment with CoCl2, the protein expression levels of HIF?1? and HIF?2? were upregulated in a CoCl2 concentration?dependent manner. The mRNA expression levels of Clock, Bmal1 and Cry2 were increased, and the mRNA expression levels of Per1, Per2, Per3, Cry1 and CKI? were decreased following CoCl2 treatment (P<0.05). In the PLC/PRF/5 cells transfected with the plasmid containing HIF?1?, the mRNA expression levels of Clock, Bmal1 and Cry2 were increased, and the mRNA expression levels of Per1, Per2, Per3, Cry1 and CKI? were decreased. In the PLC/PRF/5 cells transfected with the plasmid containing HIF?2?, the mRNA expression levels of Clock, Bmal1, Per1, Cry1, Cry2 and CKI? were upregulated, and the mRNA expression levels of Per2 and Per3 were downregulated (P<0.05). A hypoxic microenvironment may contribute to the disturbance in the expression of circadian genes in HCC. HIF?1? and HIF?2? are involved in this process and have redundant, but not identical effects. PMID:25591621

Yu, Chao; Yang, Sheng-Li; Fang, Xiefan; Jiang, Jian-Xin; Sun, Cheng-Yi; Huang, Tao

2015-05-01

353

Nonlinear dynamics of the CAM circadian rhythm in response to environmental forcing.  

PubMed

Crassulacean acid metabolism (CAM) photosynthesis functions as an endogenous circadian rhythm coupled to external environmental forcings of energy and water availability. This paper explores the nonlinear dynamics of a new CAM photosynthesis model (Bartlett et al., 2014) and investigates the responses of CAM plant carbon assimilation to different combinations of environmental conditions. The CAM model (Bartlett et al., 2014) consists of a Calvin cycle typical of C3 plants coupled to an oscillator of the type employed in the Van der Pol and FitzHugh-Nagumo systems. This coupled system is a function of environmental variables including leaf temperature, leaf moisture potential, and irradiance. Here, we explore the qualitative response of the system and the expected carbon assimilation under constant and periodically forced environmental conditions. The model results show how the diurnal evolution of these variables entrains the CAM cycle with prevailing environmental conditions. While constant environmental conditions generate either steady-state or periodically oscillating responses in malic acid uptake and release, forcing the CAM system with periodic daily fluctuations in light exposure and leaf temperature results in quasi-periodicity and possible chaos for certain ranges of these variables. This analysis is a first step in quantifying changes in CAM plant productivity with variables such as the mean temperature, daily temperature range, irradiance, and leaf moisture potential. Results may also be used to inform model parametrization based on the observed fluctuating regime. PMID:25542971

Hartzell, Samantha; Bartlett, Mark S; Virgin, Lawrence; Porporato, Amilcare

2015-03-01

354

Manipulating the sleep-wake cycle and circadian rhythms to improve clinical management of major depression  

PubMed Central

Background Clinical psychiatry has always been limited by the lack of objective tests to substantiate diagnoses and a lack of specific treatments that target underlying pathophysiology. One area in which these twin failures has been most frustrating is major depression. Due to very considerable progress in the basic and clinical neurosciences of sleep-wake cycles and underlying circadian systems this situation is now rapidly changing. Discussion The development of specific behavioral or pharmacological strategies that target these basic regulatory systems is driving renewed clinical interest. Here, we explore the extent to which objective tests of sleep-wake cycles and circadian function - namely, those that measure timing or synchrony of circadian-dependent physiology as well as daytime activity and nighttime sleep patterns - can be used to identify a sub-class of patients with major depression who have disturbed circadian profiles. Summary Once this unique pathophysiology is characterized, a highly personalized treatment plan can be proposed and monitored. New treatments will now be designed and old treatments re-evaluated on the basis of their effects on objective measures of sleep-wake cycles, circadian rhythms and related metabolic systems. PMID:23521808

2013-01-01

355

Visual responses in teleosts. Electroretinograms, eye movements, and circadian rhythms  

PubMed Central

We have recorded ocular potentials in response to brief flashes of light from two teleosts, the white perch (Roccus americana) and the green sunfish (Lepomis cyanellus). The animals were respired and maintained in an alert state for up to 2 d. Responses were recorded with corneal and transcleral electrodes. The responses of green sunfish were composed of electroretinogram (ERG) and eye movement potentials, whereas the responses in white perch contained only the ERG. Injection of curare abolished the sunfish eye movement potentials, unmasking the ERG. Observation under infrared illumination established a direct relationship between eye movements and the fast potentials which could be abolished by curare. We found no evidence of circadian changes in the amplitude of the ERG b-wave of either species. However, our results combined with those of a previous study of sunfish ocular potentials (Dearry, A., and B. Barlow, Jr. 1987. J. Gen. Physiol. 89: 745-770) suggest that the sunfish visual system exhibits rhythmic changes in oculomotor responses, which appear to be controlled by a circadian oscillator. PMID:1512556

1992-01-01

356

The Effects of Hydrogen Peroxide on the Circadian Rhythms of Microcystis aeruginosa  

PubMed Central

Background The cyanobacterium Microcystis aeruginosa is one of the principal bloom-forming cyanobacteria present in a wide range of freshwater ecosystems. M. aeruginosa produces cyanotoxins, which can harm human and animal health. Many metabolic pathways in M. aeruginosa, including photosynthesis and microcystin synthesis, are controlled by its circadian rhythms. However, whether xenobiotics affect the cyanobacterial circadian system and change its growth, physiology and biochemistry is unknown. We used real-time PCR to study the effect of hydrogen peroxide (H2O2) on the expression of clock genes and some circadian genes in M. aeruginosa during the light/dark (LD) cycle. Results The results revealed that H2O2 changes the expression patterns of clock genes (kaiA, kaiB, kaiC and sasA) and significantly decreases the transcript levels of kaiB, kaiC and sasA. H2O2 treatment also decreased the transcription of circadian genes, such as photosynthesis-related genes (psaB, psbD1 and rbcL) and microcystin-related genes (mcyA, mcyD and mcyH), and changed their circadian expression patterns. Moreover, the physiological functions of M. aeruginosa, including its growth and microcystin synthesis, were greatly influenced by H2O2 treatment during LD. These results indicate that changes in the cyanobacterial circadian system can affect its physiological and metabolic pathways. Conclusion Our findings show that a xenobiotic can change the circadian expression patterns of its clock genes to influence clock-controlled gene regulation, and these influences are evident at the level of cellular physiology. PMID:22413018

Yu, Shuqiong; Pan, Xiangjie; Wu, Tao; Fu, Zhengwei

2012-01-01

357

A two variable delay model for the circadian rhythm of Neurospora crassa.  

PubMed

A two variable model with delay in both the variables, is proposed for the circadian oscillations of protein concentrations in the fungal species Neurospora crassa. The dynamical variables chosen are the concentrations of FRQ and WC-1 proteins. Our model is a two variable simplification of the detailed model of Smolen et al. (J. Neurosci. 21 (2001) 6644) modeling circadian oscillations with interlocking positive and negative feedback loops, containing 23 variables. In our model, as in the case of Smolen's model, a sustained limit cycle oscillation takes place in both FRQ and WC-1 protein in continuous darkness, and WC-1 is anti-phase to FRQ protein, as observed in experiments. The model accounts for various characteristic features of circadian rhythms such as entrainment to light dark cycles, phase response curves and robustness to parameter variation and molecular fluctuations. Simulations are carried out to study the effect of periodic forcing of circadian oscillations by light-dark cycles. The periodic forcing resulted in a rich bifurcation diagram that includes quasiperiodicity and chaotic oscillations, depending on the magnitude of the periodic changes in the light controlled parameter. When positive feedback is eliminated, our model reduces to the generic one dimensional delay model of Lema et al. (J. Theor. Biol. 204 (2000) 565), delay model of the circadian pace maker with FRQ protein as the dynamical variable which represses its own production. This one-dimensional model also exhibits all characteristic features of circadian oscillations and gives rise to circadian oscillations which are reasonably robust to parameter variations and molecular noise. PMID:15363927

Sriram, K; Gopinathan, M S

2004-11-01

358

Effects of bile acid administration on bile acid synthesis and its circadian rhythm in man  

SciTech Connect

In man bile acid synthesis has a distinct circadian rhythm but the relationship of this rhythm to feedback inhibition by bile acid is unknown. We measured bile acid synthesis as release of 14CO2 from (26-14C)cholesterol every 2 hr in three normal volunteers during five separate 24-hr periods. Data were fitted by computer to a cosine curve to estimate amplitude and acrophase of the circadian rhythm. In an additional six volunteers, we measured synthesis every 2 hr from 8:00 a.m. to 4:00 p.m. only. During the control period, amplitude (expressed as percentage of mean synthesis) averaged 52% and acrophase averaged 6:49 a.m. During administration of ursodeoxycholic acid (15 mg per kg per day), synthesis averaged 126% of baseline (p less than 0.1), amplitude averaged 43% and acrophase averaged 6:20 a.m. During administration of chenodeoxycholic acid (15 mg per kg per day), synthesis averaged 43% of baseline (p less than 0.001), amplitude averaged 53% and acrophase averaged 9:04 a.m. Addition of prednisone to this regimen of chenodeoxycholic acid to eliminate release of 14CO2 from corticosteroid hormone synthesis resulted in a mean amplitude of 62% and a mean acrophase of 6:50 a.m., values very similar to those in the baseline period. Administration of prednisone alone also did not significantly alter the baseline amplitude (40%) or acrophase (6:28 a.m.). We conclude that neither chenodeoxycholic acid nor ursodeoxycholic acid significantly alters the circadian rhythm of bile acid synthesis in man.

Pooler, P.A.; Duane, W.C.

1988-09-01

359

Effects of long-term microgravity exposure in space on circadian rhythms of heart rate variability.  

PubMed

We evaluated their circadian rhythms using data from electrocardiographic records and examined the change in circadian period related to normal RR intervals for astronauts who completed a long-term (?6-month) mission in space. The examinees were seven astronauts, five men and two women, from 2009 to 2010. Their mean?±?SD age was 52.0?±?4.2 years (47-59?yr). Each stayed in space for more than 160 days; their average length of stay was 172.6?±?14.6 days (163-199 days). We conducted a 24-h Holter electrocardiography before launch (Pre), at one month after launch (DF1), at two months after launch (DF2), at two weeks before return (DF3), and at three months after landing (Post), comparing each index of frequency-domain analysis and 24-h biological rhythms of the NN intervals (normal RR intervals). Results show that the mean period of Normal Sinus (NN) intervals was within 24?±?4?h at each examination. Inter-individual variability differed among the stages, being significantly smaller at DF3 (Pre versus DF1 versus DF3 versus Post?=?22.36?±?2.50 versus 25.46?±?4.37 versus 22.46?±?1.75 versus 26.16?±?7.18?h, p?circadian rhythms were disturbed until one month had passed in space, well-scheduled sleep and wake rhythms and meal times served as synchronizers. PMID:25392280

Yamamoto, Naomune; Otsuka, Kuniaki; Kubo, Yutaka; Hayashi, Mitsutoshi; Mizuno, Koh; Ohshima, Hiroshi; Mukai, Chiaki

2015-04-01

360

A Study of Circadian Rhythm and Meteorological Factors Influencing Acute Myocardial Infarction  

E-print Network

The circadian rhythm in the occurrence of acute myocardial infarction (AMI) was assessed in three hundred and twenty three patients admitted with AMI during the two-year period June 1992 to May 1994. The influence of the following meteorological, solar-geophysical and cosmic parameters in the causation of an infarct was also considered : (1) surface pressure (2) maximum temperature (3) minimum temperature (4) relative humidity (5) cosmic ray index (6) geomagnetic aa index (7) solar flares and (8) sunspot number. A well pronounced diurnal variability in AMI with a peak in the morning hours (6-12 a.m.) was seen. Further analysis of the data by considering one-hour periods revealed the presence of a smaller evening (10 p.m.) increase in incidence, i.e., the existence of a bimodal circadian rhythm. The simultaneous occurrence of the well documented semi-diurnal rhythm in surface pressure and incidence of acute myocardial infarction were evident. This may be one of the factors involved in the causation of the smaller evening peak-the reasons for which were unclear till now. Month-to-month variation in surface pressure was also found to be significantly correlated with incidence of acute myocardial infarction. Recognition of a circadian rhythm in the onset of AMI suggests the need for enhanced pharmacological protection during the vulnerable periods. Significant correlations were also found between monthly incidence of AMI and month-to-month variation of cosmic ray index and solar flare counts. The pattern of incidence of AMI was seen to be modified by full moon and new moon. There was no association between maximum temperature, minimum temperature or relative humidity and incidence of AMI.

A. M. Selvam; D. Sen; S. M. S. Mody

1998-12-08

361

Circadian rhythm of mechanically mediated differentiation of osteoblasts  

NASA Technical Reports Server (NTRS)

The differential of osteoblasts in response to orthodontic pressure in the periodontal ligament of the maxillary-first-molar periodontal ligaments of 12-h-light/dark-entrained 7-wk-old male Simonsen outbred rats is measured by (H-3)-Thymidine nuclear-volume morphometry (Roberts et al., 1983) at hourly intervals throughout the circadian cycle. The results are presented in graphs and discussed. Preosteoblast large nuclei (D-cells) are found to synthesize DNA mainly in light and to divide in the following dark period, while small-nucleus osteoprogenitors (A-cells) synthesize in darkness and divide in light. These findings are seen as consistent with a model in which the sequence of proliferation and differentiation requires at least 60 h (five 12-h periods) and the shift from A to D cells lasts about 19 h.

Roberts, W. E.; Mozsary, P. G.; Klingler, E.

1984-01-01

362

Pigment dispersing hormone modulates spontaneous electrical activity of the cerebroid ganglion and synchronizes electroretinogram circadian rhythm in crayfish Procambarus clarkii.  

PubMed

In crayfish, one very well-studied circadian rhythm is that of electroretinogram (ERG) amplitude. The cerebroid ganglion has been considered a plausible site for the circadian pacemaker of this rhythm and for the retinular photoreceptors, as the corresponding effectors. The pigment dispersing hormone (PDH) appears to synchronize ERG rhythm, but its characterization as a synchronizer cue remains incomplete. The main purposes of this work were a) to determine whether PDH acts on the cerebroid ganglion, and b) to complete its characterization as a non-photic synchronizer. Here we show that PDH increases the number of the spontaneous potentials of the cerebroid ganglion, reaching 149.92±6.42% of the activity recorded in the controls, and that daily application of PDH for 15 consecutive days adjusts the ERG circadian rhythm period to 24.0±0.2h and the end of the activity period of the rhythm coincides with the injection of the hormone. In this work, we hypothesized that in crayfish, PDH transmits the "day" signal to the ERG circadian system and acts upon both the presumptive circadian pacemaker and the corresponding effectors to reinforce the synchronization of the system. PMID:22252127

Solís-Chagoyán, Héctor; Alvarado, Ramón; Figueroa, Alejandra; Mendoza-Vargas, Leonor; Fuentes-Pardo, Beatriz

2012-04-01

363

Disruption of cardiovascular circadian rhythms in mice post myocardial infarction: relationship with central angiotensin II receptor expression  

PubMed Central

Abstract Angiotensin II (Ang II) is well known to participate in the abnormal autonomic cardiovascular control that occurs during the development of chronic heart failure (CHF). Disrupted cardiovascular circadian rhythm in CHF is also well accepted; however, the mechanisms underlying and the role of central Ang II type 1 receptors (AT1R) and oxidative stress in mediating such changes are not clear. In a post myocardial infarction (MI) CHF mouse model we investigated the circadian rhythm for mean arterial pressure (MAP), heart rate (HR), and baroreflex sensitivity (BRS) following MI. The cardiovascular parameters represent the middle 6?h averages during daytime (6:00–18:00) and nighttime (18:00–6:00). HR increased with the severity of CHF reaching its maximum by 12 weeks post?MI; loss of circadian HR and BRS rhythms were observed as early as 4 weeks post?MI in conjunction with a significant blunting of the BRS and an upregulation in the AT1R and gp91phox proteins in the brainstem. Loss of MAP circadian rhythm was observed 8 weeks post?MI. Circadian AT1R expression was demonstrated in sham animals but was lost 8 weeks following MI. Losartan reduced AT1R expression in daytime (1.18 ± 0.1 vs. 0.85 ± 0.1; P < 0.05) with a trend toward a reduction in the AT1R mRNA expression in the nighttime (1.2 ± 0.1 vs. 1.0 ± 0.1; P > 0.05) but failed to restore circadian variability. The disruption of circadian rhythm for HR, MAP and BRS along with the upregulation of AT1 and gp91phox suggests a possible role for central oxidative stress as a mediator of circadian cardiovascular parameters in the post?MI state. PMID:25413327

Mousa, Tarek M.; Schiller, Alicia M.; Zucker, Irving H.

2014-01-01

364

Improvement of Circadian Rhythm of Heart Rate Variability by Eurythmy Therapy Training  

PubMed Central

Background. Impairment of circadian rhythm is associated with various clinical problems. It not only has a negative impact on quality of life but can also be associated with a significantly poorer prognosis. Eurythmy therapy (EYT) is an anthroposophic movement therapy aimed at reducing fatigue symptoms and stress levels. Objective. This analysis of healthy subjects was conducted to examine whether the improvement in fatigue symptoms was accompanied by improvements in the circadian rhythm of heart rate variability (HRV). Design. Twenty-three women performed 10 hours of EYT over six weeks. Electrocardiograms (ECGs) were recorded before and after the EYT trial. HRV was quantified by parameters of the frequency and time domains and the nonlinear parameters of symbolic dynamics. Results. The day-night contrast with predominance of vagal activity at night becomes more pronounced after the EYT training, and with decreased Ultralow and very low frequencies, the HRV shows evidence of calmer sleep. During the night, the complexity of the HRV is significantly increased indicated by nonlinear parameters. Conclusion. The analysis of the circadian patterns of cardiophysiological parameters before and after EYT shows significant improvements in HRV in terms of greater day-night contrast caused by an increase of vagal activity and calmer and more complex HRV patterns during sleep. PMID:23533496

Seifert, Georg; Kanitz, Jenny-Lena; Pretzer, Kim; Henze, Günter; Witt, Katharina; Reulecke, Sina; Voss, Andreas

2013-01-01

365

Altered Circadian Rhythm and Metabolic Gene Profile in Rats Subjected to Advanced Light Phase Shifts  

PubMed Central

The circadian clock regulates metabolic homeostasis and its disruption predisposes to obesity and other metabolic diseases. However, the effect of phase shifts on metabolism is not completely understood. We examined whether alterations in the circadian rhythm caused by phase shifts induce metabolic changes in crucial genes that would predispose to obesity. Three-month-old rats were maintained on a standard diet under lighting conditions with chronic phase shifts consisting of advances, delays or advances plus delays. Serum leptin, insulin and glucose levels decreased only in rats subjected to advances. The expression of the clock gene Bmal 1 increased in the hypothalamus, white adipose tissue (WAT), brown adipose tissue (BAT) and liver of the advanced group compared to control rats. The advanced group showed an increase in hypothalamic AgRP and NPY mRNA, and their lipid metabolism gene profile was altered in liver, WAT and BAT. WAT showed an increase in inflammation and ER stress and brown adipocytes suffered a brown-to-white transformation and decreased UCP-1 expression. Our results indicate that chronic phase advances lead to significant changes in neuropeptides, lipid metabolism, inflammation and ER stress gene profile in metabolically relevant tissues such as the hypothalamus, liver, WAT and BAT. This highlights a link between alteration of the circadian rhythm and metabolism at the transcriptional level. PMID:25837425

Herrero, Laura; Valcarcel, Lorea; da Silva, Crhistiane Andressa; Albert, Nerea; Diez-Noguera, Antoni; Cambras, Trinitat; Serra, Dolors

2015-01-01

366

Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms  

NASA Technical Reports Server (NTRS)

Circadian rhythms of activity (Act) and body temperature (Tb) were recorded from male Syrian hamsters under square-wave (LDSq) and simulated natural (LDSN, with dawn and dusk transitions) light-dark cycles. Light intensity and data sampling were under the synchronized control of a laboratory computer. Changes in reactive and predictive onsets and offsets for the circadian rhythms of Act and Tb were examined in both lighting conditions. The reactive Act onset occurred 1.1 h earlier (P < 0.01) in LDSN than in LDSq and had a longer alpha-period (1.7 h; P < 0.05). The reactive Tb onset was 0.7 h earlier (P < 0.01) in LDSN. In LDSN, the predictive Act onset advanced by 0.3 h (P < 0.05), whereas the Tb predictive onset remained the same as in LDSq. The phase angle difference between Act and Tb predictive onsets decreased by 0.9 h (P < 0.05) in LDSN, but the offsets of both measures remained unchanged. In this study, animals exhibited different circadian entrainment characteristics under LDSq and LDSN, suggesting that gradual and abrupt transitions between light and dark may provide different temporal cues.

Tang, I. H.; Murakami, D. M.; Fuller, C. A.

1999-01-01

367

How might circadian rhythms control mood? Let me count the ways…..  

PubMed Central

Mood disorders are serious diseases that affect a large portion of the population. There have been many hypotheses put forth over the years to explain the development of major depression (MDD), bipolar disorder (BD) and other mood disorders. These hypotheses include disruptions in monoamine transmission, HPA axis function, immune function, neurogenesis, mitochondrial dysfunction and neuropeptide signaling (to name a few). Nearly all people suffering from mood disorders have significant disruptions in circadian rhythms and the sleep/wake cycle. In fact altered sleep patterns are one of the major diagnostic criteria for these disorders. Moreover, environmental disruptions to circadian rhythms including shift work, travel across time zones, and irregular social schedules tend to precipitate or exacerbate mood-related episodes. Recent studies have found that molecular clocks are found throughout the brain and body where they participate in the regulation of most physiological processes, including those thought to be involved in mood regulation. This review will summarize recent data which implicates the circadian system as a vital regulator of a variety of systems which are thought to play a role in the development of mood disorders. PMID:23558300

McClung, Colleen A.

2013-01-01

368

Circadian cycles are the dominant transcriptional rhythm in the intertidal mussel Mytilus californianus  

PubMed Central

Residents in the marine intertidal, the zone where terrestrial and marine habitats converge, inhabit an environment that is subject to both the 24-h day and night daily rhythm of the terrestrial earth and also the 12.4-h ebb and flow of the tidal cycle. Here, we investigate the relative contribution of the daily and tidal cycle on the physiology of intertidal mussels, Mytilus californianus, by monitoring rhythms of gene expression in both simulated and natural tidal environments. We report that >40% of the transcriptome exhibits rhythmic gene expression, and that depending on the specific tidal conditions, between 80% and 90% of the rhythmic transcripts follow a circadian expression pattern with a period of 24 to 26 h. Consistent with the dominant effect of the circadian cycle we show that the expression of clock genes oscillates with a 24-h period. Our data indicate that the circadian 24-h cycle is the dominant driver of rhythmic gene expression in this intertidal inhabitant despite the profound environmental and physiological changes associated with aerial exposure during tidal emergence. PMID:21911390

Connor, Kwasi M.; Gracey, Andrew Y.

2011-01-01

369

The parathyroid hormone circadian rhythm is truly endogenous--a general clinical research center study  

NASA Technical Reports Server (NTRS)

While circulating levels of PTH follow a diurnal pattern, it has been unclear whether these changes are truly endogenous or are dictated by external factors that themselves follow a diurnal pattern, such as sleep-wake cycles, light-dark cycles, meals, or posture. We evaluated the diurnal rhythm of PTH in 11 normal healthy male volunteers in our Intensive Physiologic Monitoring Unit. The first 36 h spent under baseline conditions were followed by 28-40 h of constant routine conditions (CR; enforced wakefulness in the strict semirecumbent position, with the consumption of hourly snacks). During baseline conditions, PTH levels followed a bimodal diurnal rhythm with an average amplitude of 4.2 pg/mL. A primary peak (t1max) occurred at 0314 h, and the secondary peak (t2max) occurred at 1726 h, whereas the primary and secondary nadirs (t1min and t2min) took place, on the average, at 1041 and 2103 h, respectively. This rhythm was preserved under CR conditions, albeit with different characteristics, thus confirming its endogenous nature. The serum ionized calcium (Cai) demonstrated a rhythm in 3 of the 5 subjects studied that varied widely between individuals and did not have any apparent relation to PTH. Urinary calcium/creatinine (UCa/Cr), phosphate/Cr (UPO4/Cr), and sodium/Cr (UNa/Cr) ratios all followed a diurnal rhythm during the baseline day. These rhythms persisted during the CR, although with different characteristics for the first two parameters, whereas that of UNa/Cr was unchanged. In general, the temporal pattern for the UCa/Cr curve was a mirror image of the PTH curve, whereas the UPO4/Cr pattern moved in parallel with the PTH curve. In conclusion, PTH levels exhibit a diurnal rhythm that persists during a CR, thereby confirming that a large component of this rhythm is an endogenous circadian rhythm. The clinical relevance of this rhythm is reflected in the associated rhythms of biological markers of PTH effect at the kidney, namely UCa/Cr and UPO4/Cr.

el-Hajj Fuleihan, G.; Klerman, E. B.; Brown, E. N.; Choe, Y.; Brown, E. M.; Czeisler, C. A.

1997-01-01

370

Corkscrews and singularities in fruitflies - Resetting behavior of the circadian eclosion rhythm.  

NASA Technical Reports Server (NTRS)

Description of experiments undertaken to define the phase-resetting behavior of the circadian rhythm of pupal eclosion in populations of fruitflies. An attempt is made to determine how and why the resetting response depends on the duration of a standard perturbation as well as on the time at which it is given. Plotting a three-dimensional graph of the measured emergence centroids vs the stimulus variables, the data are found to spiral up around a vertical rotation axis. Using a computer, a smooth surface, called the resetting surface, which approximately fits the helicoidal cloud of data points, is obtained and is shown to be best described as a vertical corkscrew linking together tilted planes. This corkscrew feature of the resetting surface is taken to indicate that there is an isolated perturbation following which there is either no circadian rhythm of emergence in the steady state, or one of unpredictable phase. A hypothesis concerning the clock dynamics underlying the eclosion rhythm is briefly sketched which encompasses the main features of known resetting data using single discrete pulses of any perturbing agent.

Winfree, A. T.

1971-01-01

371

Seasonal variations in circadian rhythms persist in gonadectomized golden-mantled ground squirrels.  

PubMed

Circadian wheel-running activity was monitored in intact and gonadectomized female and male golden-mantled ground squirrels maintained in a 14L:10D photoperiod at 21 degrees C. Marked advances in phase angle of activity onset and increases in the duration of the daily active phase occurred each year in intact animals coincident with the phase of reproductive activity. Surprisingly, long-term gonadectomized squirrels of both sexes manifested similar seasonal changes in the circadian system. Seasonal circadian variations in locomotor activity are generated by a circannual clock independent from and not influenced by concurrent changes in secretion of gonadal hormones. PMID:7488757

Lee, T M; Zucker, I

1995-09-01

372

Does Disruption of Circadian Rhythms Contribute to Beta-Cell Failure in Type 2 Diabetes?  

PubMed Central

Type 2 diabetes mellitus (T2DM) is a complex metabolic disease characterized by the loss of beta-cell secretory function and mass. The pathophysiology of beta-cell failure in T2DM involves a complex interaction between genetic susceptibilities and environmental risk factors. One environmental condition that is gaining greater appreciation as a risk factor for T2DM is the disruption of circadian rhythms (eg, shift-work and sleep loss). In recent years, circadian disruption has become increasingly prevalent in modern societies and consistently shown to augment T2DM susceptibility (partly mediated through its effects on pancreatic beta-cells). Since beta-cell failure is essential for development of T2DM, we will review current work from epidemiologic, clinical, and animal studies designed to gain insights into the molecular and physiological mechanisms underlying the predisposition to beta-cell failure associated with circadian disruption. Elucidating the role of circadian clocks in regulating beta-cell health will add to our understanding of T2DM pathophysiology and may contribute to the development of novel therapeutic and preventative approaches. PMID:24532160

Rakshit, Kuntol; Thomas, Anthony P.

2014-01-01

373

Circadian rhythms and enhanced athletic performance in the National Football League.  

PubMed

Circadian rhythms produce daily changes in critical elements of athletic performance. We explored the significance of performing at different circadian times in the National Football League (NFL) over the last 25 seasons. West Coast (WC) NFL teams should have a circadian advantage over East Coast (EC) teams during Monday Night Football (MNF) games because WC teams are essentially playing closer to the proposed peak athletic performance time of day. Retrospective data analysis was applied to all games involving WC versus EC teams playing on MNF with start times of 9:00 p.m. Eastern Standard Time (EST) from the 1970-1994 seasons. Logistic regression analysis of win-loss records relative to point spreads and home-field advantage was examined. West Coast teams win more often (p < 0.01) and by more points per game than EC teams. West Coast teams are performing significantly (p < 0.01) better than is predicted by the Las Vegas odds (the point spread). This apparent advantage enhances home-field advantage for WC teams and essentially eliminates the beneficial effects of home-field advantage for EC teams during MNF games. These results support the presence of an enhancement of athletic performance at certain circadian times of the day. PMID:9381059

Smith, R S; Guilleminault, C; Efron, B

1997-05-01

374

Does disruption of circadian rhythms contribute to beta-cell failure in type 2 diabetes?  

PubMed

Type 2 diabetes mellitus (T2DM) is a complex metabolic disease characterized by the loss of beta-cell secretory function and mass. The pathophysiology of beta-cell failure in T2DM involves a complex interaction between genetic susceptibilities and environmental risk factors. One environmental condition that is gaining greater appreciation as a risk factor for T2DM is the disruption of circadian rhythms (eg, shift-work and sleep loss). In recent years, circadian disruption has become increasingly prevalent in modern societies and consistently shown to augment T2DM susceptibility (partly mediated through its effects on pancreatic beta-cells). Since beta-cell failure is essential for development of T2DM, we will review current work from epidemiologic, clinical, and animal studies designed to gain insights into the molecular and physiological mechanisms underlying the predisposition to beta-cell failure associated with circadian disruption. Elucidating the role of circadian clocks in regulating beta-cell health will add to our understanding of T2DM pathophysiology and may contribute to the development of novel therapeutic and preventative approaches. PMID:24532160

Rakshit, Kuntol; Thomas, Anthony P; Matveyenko, Aleksey V

2014-04-01

375

Circadian rhythm of periodic limb movements and sensory symptoms of restless legs syndrome.  

PubMed

The symptoms of restless legs syndrome (RLS) worsen while patients are sitting or lying and also worsen at night. The current study was designed to determine if the periodic limb movements (PLMs) and sensory symptoms of RLS are modulated by an independent circadian factor. We recorded sleeping and waking PLMs and waking sensory symptoms in eight volunteers with RLS for 3 successive nights and days, starting with a polysomnographic recording of 2 nights, followed by a third night of sleep deprivation and the day after sleep deprivation. This study showed that both the PLMs and sensory symptoms were worst at night with a maximum for both between midnight and 1:00 AM and a minimum between 9:00 and 11:00 AM. Sleep and drowsiness had a tendency to worsen PLMs and sensory symptoms after the night of sleep deprivation. Circadian temperature curves were normal in all four patients with adequate data collection. The highest PLM counts occurred on the falling phase of the circadian temperature curve whereas the lowest PLM counts occurred on the rising phase of the curve. We conclude that the PLM and sensory symptoms in RLS are influenced by a circadian rhythm, and that the "worsening at night" criterion of the RLS Definition Criteria is, at least in part, distinct from the "worsening while lying or sitting" criterion. PMID:9918351

Trenkwalder, C; Hening, W A; Walters, A S; Campbell, S S; Rahman, K; Chokroverty, S

1999-01-01

376

Circadian rhythms of hydraulic conductance and growth are enhanced by drought and improve plant performance  

PubMed Central

Circadian rhythms enable plants to anticipate daily environmental variations, resulting in growth oscillations under continuous light. Because plants daily transpire up to 200% of their water content, their water status oscillates from favourable during the night to unfavourable during the day. We show that rhythmic leaf growth under continuous light is observed in plants that experience large alternations of water status during an entrainment period, but is considerably buffered otherwise. Measurements and computer simulations show that this is due to oscillations of plant hydraulic conductance and plasma membrane aquaporin messenger RNA abundance in roots during continuous light. A simulation model suggests that circadian oscillations of root hydraulic conductance contribute to acclimation to water stress by increasing root water uptake, thereby favouring growth and photosynthesis. They have a negative effect in favourable hydraulic conditions. Climate-driven control of root hydraulic conductance therefore improves plant performances in both stressed and non-stressed conditions. PMID:25370944

Caldeira, Cecilio F.; Jeanguenin, Linda; Chaumont, François; Tardieu, François

2014-01-01

377

Control mechanisms of circadian rhythms in body composition: Implications for manned spaceflight  

NASA Technical Reports Server (NTRS)

The mechanisms that underlie the circadian variations in electrolyte content in body fluid compartments were investigated, and the mechanisms that control the oscillations were studied in order to investigate what effects internal desynchronization in such a system would have during manned space flight. The studies were performed using volunteer human subjects and squirrel monkeys. The intercompartmental distribution of potassium was examined when dietary intake, activity, and posture are held constant throughout each 24-hour day. A net flux of potassium was observed out of the body cell mass during the day and a reverse flux from the extracellular fluid into the body cell mass during the night, counterbalanced by changes in urinary potassium excretion. Experiments with monkeys provided evidence for the synchronization of renal potassium excretion by the rhythm of cortisol secretion with the light-dark cycle. Three models of the circadian timing system were formalized.

Ede, M. C. M.

1975-01-01

378

Dynamics of three coupled van der Pol oscillators with application to circadian rhythms  

NASA Astrophysics Data System (ADS)

In this work we study a system of three van der Pol oscillators. Two of the oscillators are identical, and are not directly coupled to each other, but rather are coupled via the third oscillator. We investigate the existence of the in-phase mode in which the two identical oscillators have the same behavior. To this end we use the two variable expansion perturbation method (also known as multiple scales) to obtain a slow flow, which we then analyze using the computer algebra system MACSYMA and the numerical bifurcation software AUTO. Our motivation for studying this system comes from the presence of circadian rhythms in the chemistry of the eyes. We model the circadian oscillator in each eye as a van der Pol oscillator. Although there is no direct connection between the two eyes, they are both connected to the brain, especially to the pineal gland, which is here represented by a third van der Pol oscillator.

Rompala, Kevin; Rand, Richard; Howland, Howard

2007-08-01

379

Effect of feeding and temperature on the circadian rhythms of cortisol, thyroxine and triiodothyronine in pigs  

SciTech Connect

An experiment was conducted to evaluate the circadian rhythms of cortisol, thyroxine (T/sub 4/) and triiodothyronine (T/sub 3/) in pigs under two temperature and feeding regimes. Twenty-eight barrows were randomly assigned to one of the following: 1) ad-libitum fed at 5/sup 0/C(AL-5); 2) ad-libitum fed at 20/sup 0/C(AL-20); 3) meal fed at 5/sup 0/C(M-5); and 4) meal fed at 20/sup 0/C(M-20). M-5 and M-20 animals were fed at 0730 and 1400 hrs. Lights were on from 0600 to 2000 hrs. After 5 wks, blood samples were collected for 27 hrs. Serum cortisol, T/sub 4/ and T/sub 3/ concentrations were determined by RIA. No significant differences were found in the mesors, amplitudes or acrophases for cortisol. The mesors for T/sub 4/ (p<.01) were 60.6 +/- 5.6, 40.2 +/- 5.6, 61.2 +/- 5.6 and 49.1 +/- 5.0 ng/ml for AL-5, AL-20, M-5, and M-20, respectively. The mesors for T/sub 3/ (p<.01) were .85 +/- .06, .69 +/- .06, .92 +/- .06 and .66 +/- .05 ng/ml for AL-5, AL-20, M-5, and M-20 respectively. No differences in the amplitudes or acrophases for T/sub 3/ or T/sub 4/ were found. These data show that temperature and feeding regimes do not entrain the circadian rhythm of cortisol in pigs. The circadian rhythms of T/sub 4/ and T/sub 3/ are also not altered by feeding regimes but are affected by temperature.

Becker, B.A.; Nienaber, J.A.; Ford, J.J.; Hahn, G.L.

1986-03-05

380

Wrist actimetry circadian rhythm as a robust predictor of colorectal cancer patients survival.  

PubMed

The disruption of the circadian timing system (CTS), which rhythmically controls cellular metabolism and proliferation, accelerated experimental cancer progression. A measure of CTS function in cancer patients could thus provide novel prediction information for outcomes, and help to identify novel specific therapies. The rest-activity circadian rhythm is a reliable and non-invasive CTS biomarker, which was monitored using a wrist watch accelerometer for 2 days in 436 patients with metastatic colorectal cancer. The relative percentage of activity in-bed versus out-of-bed (I < O) constituted the tested CTS measure, whose prognostic value for overall survival (OS) and progression-free survival (PFS) was determined in a pooled analysis of three patient cohorts with different treatment exposures. Median OS was 21.6 months [17.8-25.5] for patients with I < O above the median value of 97.5% as compared to 11.9 months [10.4-13.3] for those with a lower I < O (Log-rank p < 0.001). Multivariate analyses retained continuous I < O as a joint predictor of both OS and PFS, with respective hazard ratios (HR) of 0.954 (p < 0.001) and 0.970 (p < 0.001) for each 1% increase in I < O. HRs had similar values in all the patient subgroups tested. The circadian physiology biomarker I < O constitutes a robust and independent quantitative predictor of cancer patient outcomes, that can be easily and cost-effectively measured during daily living. Interventional studies involving 24-h schedules of clock-targeted drugs, light intensity, exercise and/or meals are needed for testing the relevance of circadian synchronization for the survival of patients with disrupted rhythms. PMID:24927369

Lévi, Francis; Dugué, Pierre-Antoine; Innominato, Pasquale; Karaboué, Abdoulaye; Dispersyn, Garance; Parganiha, Arti; Giacchetti, Sylvie; Moreau, Thierry; Focan, Christian; Waterhouse, Jim; Spiegel, David

2014-10-01

381

Advancing Circadian Rhythms Before Eastward Flight: A Strategy to Prevent or Reduce Jet Lag  

PubMed Central

Study Objectives To develop a practical pre-eastward flight treatment to advance circadian rhythms as much as possible but not misalign them with sleep. Design One group had their sleep schedule advanced by 1 hour per day and another by 2 hours per day. Setting Baseline at home, treatment in lab. Participants Young healthy adults (11 men, 15 women) between the ages of 22 and 36 years. Interventions Three days of a gradually advancing sleep schedule (1 or 2 hours per day) plus intermittent morning bright light (one-half hour ~5000 lux, one-half hour of < 60 lux) for 3.5 hours. Measurements and Results The dim light melatonin onset was assessed before and after the 3-day treatment. Subjects completed daily sleep logs and symptom questionnaires and wore wrist activity monitors. The dim light melatonin onset advanced more in the 2-hours-per-day group than in the 1-hour-per-day group (median phase advances of 1.9 and 1.4 hours), but the difference between the means (1.8 and 1.5 hours) was not statistically significant. By the third treatment day, circadian rhythms were misaligned relative to the sleep schedule, and subjects had difficulty falling asleep in the 2-hours-per-day group, but this was not the case in the 1-hour-per-day group. Nevertheless, the 2-hours-per-day group did slightly better on the symptom questionnaires. In general, sleep disturbance and other side effects were small. Conclusions A gradually advancing sleep schedule with intermittent morning bright light can be used to advance circadian rhythms before eastward flight and, thus, theoretically, prevent or reduce subsequent jet lag. Given the morning light treatment used here, advancing the sleep schedule 2 hours per day is not better than advancing it 1 hour per day because it was too fast for the advance in circadian rhythms. A diagram is provided to help the traveler plan a preflight schedule. PMID:15700719

Eastman, Charmane I.; Gazda, Clifford J; Burgess, Helen J.; Crowley, Stephanie J.; Fogg, Louis F.

2005-01-01

382

The pineal clock affects behavioral circadian rhythms but not photoperiodic induction in the Indian weaver bird ( Ploceus philippinus )  

Microsoft Academic Search

We investigated whether pineal is part of the circadian clock system which regulates circadian rhythms of activity and photosensitivity\\u000a in the Indian weaver bird (Ploceus philippinus). Two experiments were performed. The first experiment examined the induction of testicular growth, and androgen-dependent\\u000a beak pigmentation and luteinizing hormone (LH)-specific plumage coloration in pinealectomised (pinx) and sham-operated (sham)\\u000a birds exposed to short day

Sangeeta Rani; Sudhi Singh; Vinod Kumar

2005-01-01

383

Open Questions on Mind, Genes, Consciousness, and Behavior: The Circadian and Ultradian Rhythms of Art, Beauty, and Truth in Creativity  

Microsoft Academic Search

An earlier companion volume to this text ended with an epilogue on “The Unification Hypothesis of Chronobiology from Molecule\\u000a to Mind” wherein we traced the evolution of life and mind as manifest in our circadian and ultradian psychobiology (Lloyd\\u000a and Rossi, 1992). This chapter extends that broad scenario by reviewing the circadian and ultradian rhythms of gene expression,\\u000a brain plasticity,

E. L. Rossi; K. L. Rossi

384

Melatonin and the circadian rhythms of feeding and perch-hopping in the European starling, Sturnus vulgaris  

Microsoft Academic Search

The role of melatonin plasma titers in the control of free-running circadian rhythms was investigated in European starlings,Sturnus vulgaris, held in continuous dim light. Simultaneous recordings of plasma melatonin, perch-hopping and feeding activity revealed synchronous circadian variations in all three functions with high melatonin titers during resting and low titers during activity periods. Implanting birds with melatonin silastic capsules resulted

Hans J. A. Beldhuis; John P. Dittami; Eberhard Gwinner

1988-01-01

385

Circadian Rhythm Sleep Disorders: Part II, Advanced Sleep Phase Disorder, Delayed Sleep Phase Disorder, Free-Running Disorder, and Irregular Sleep-Wake Rhythm  

PubMed Central

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. Citation: Sack R; Auckley D; Auger RR; Carskadon MA; Wright KP; Vitiello MV; Zhdanova IV. Circadian rhythm sleep disorders: Part II, advanced sleep phase disorder, delayed sleep phase disorder, free-running disorder, and irregular sleep-wake rhythm. SLEEP 2007;30(11):1484-1501. PMID:18041481

Sack, Robert L; Auckley, Dennis; Auger, R. Robert; Carskadon, Mary A.; Wright, Kenneth P.; Vitiello, Michael V.; Zhdanova, Irina V.

2007-01-01

386

Circadian rhythm of plasma and urinary angiotensinogen in healthy volunteers and in patients with chronic kidney disease  

PubMed Central

The urinary angiotensinogen (AGT) excretion rate could be a novel biomarker for the intrarenal activity of the reninangiotensin system. Little is known about the circadian rhythm of AGT levels in plasma or urine. In this short article, making use of data in plasma and urine of healthy volunteers and patients with chronic kidney diseases, we first report that we were unable to find evidence for a circadian rhythm of AGT under any condition. Next we critically discuss to what degree elevated urinary AGT levels might be considered an independent biomarker that is not simply the non-specific consequence of proteinuria. PMID:25381307

Nishijima, Yoko; Kobori, Hiroyuki; Kaifu, Kumiko; Mizushige, Tomoko; Hara, Taiga; Nishiyama, Akira; Kohno, Masakazu

2014-01-01

387

Circadian rhythms of PERIOD1 expression in the dorsomedial hypothalamic nucleus in the absence of entrained food-anticipatory activity rhythms in rats.  

PubMed

When food availability is restricted to a single time of day, circadian rhythms of behavior and physiology in rodents shift to anticipate the predictable time of food arrival. It has been hypothesized that certain food-anticipatory rhythms are linked to the induction and entrainment of rhythms in clock gene expression in the dorsomedial hypothalamic nucleus (DMH), a putative food-entrained circadian oscillator. To study this concept further, we made food availability unpredictable by presenting the meal at a random time each day (variable restricted feeding, VRF), either during the day, night or throughout the 24-h cycle. Wheel running activity and the expression of the clock protein, Period1 (PER1), in the DMH and the suprachiasmatic nucleus (SCN) were assessed. Rats exhibited increased levels of activity during the portion of the day when food was randomly presented but, as expected, failed to entrain anticipatory wheel running activity to a single time of day. PER1 expression in the SCN was unchanged by VRF schedules. In the DMH, PER1 expression became rhythmic, peaking at opposite times of day in rats fed only during the day or during the night. In rats fed randomly throughout the entire 24-h cycle, PER1 expression in the DMH remained arrhythmic, but was elevated. These results demonstrate that VRF schedules confined to the day or night can induce circadian rhythms of clock gene expression in the DMH. Such feeding schedules cannot entrain behavioral rhythms, thereby showing that food-entrainment of behavior and circadian rhythms of clock gene expression in the DMH are dissociable. PMID:19490091

Verwey, Michael; Lam, Germain Y M; Amir, Shimon

2009-06-01

388

Two-oscillator structure of the pacemaker controlling the circadian rhythm of N-acetyltransferase in the rat pineal gland  

Microsoft Academic Search

1.The organization of the pacemaker driving the circadian rhythm of N-acetyltransferase activity in the rat pineal gland was studied by observing changes of the rhythm caused by 1 min light pulses applied at night. These pulses proved to be effective phase-shifting signals.2.After 1 min light pulses applied in the first half of the night. N-acetyltransferase activity began to increase anew

Helena Illnerová; Ji?í Van??ek

1982-01-01

389

Properties of the Aplysia visual system: in vitro entrainment of the circadian rhythm and centrifugal regulation of the eye  

Microsoft Academic Search

1.Properties of the visual system of Aplysia californica were studied by recording optic nerve impulses extracellularly from isolated eyes in constant darkness.2.In vivo entrainment of the circadian rhythm of afferent optic nerve impulses by LD 12:12 cycles phase advanced 13 hours was essentially complete after only one exposure of the animal to this light cycle.3.The impulse rhythms of eyes exposed

Arnold Eskin

1971-01-01

390

Circadian Rhythms of Sense and Antisense Transcription in Sugarcane, a Highly Polyploid Crop  

PubMed Central

Commercial sugarcane (Saccharum hybrid) is a highly polyploid and aneuploid grass that stores large amounts of sucrose in its stem. We have measured circadian rhythms of sense and antisense transcription in a commercial cultivar (RB855453) using a custom oligoarray with 14,521 probes that hybridize to sense transcripts (SS) and 7,380 probes that hybridize to antisense transcripts (AS).We estimated that 32% of SS probes and 22% AS probes were rhythmic. This is a higher proportion of rhythmic probes than the usually found in similar experiments in other plant species. Orthologs and inparalogs of Arabidopsis thaliana, sugarcane, rice, maize and sorghum were grouped in ortholog clusters. When ortholog clusters were used to compare probes among different datasets, sugarcane also showed a higher proportion of rhythmic elements than the other species. Thus, it is possible that a higher proportion of transcripts are regulated by the sugarcane circadian clock. Thirty-six percent of the identified AS/SS pairs had significant correlated time courses and 64% had uncorrelated expression patterns. The clustering of transcripts with similar function, the anticipation of daily environmental changes and the temporal compartmentation of metabolic processes were some properties identified in the circadian sugarcane transcriptome. During the day, there was a dominance of transcripts associated with photosynthesis and carbohydrate metabolism, including sucrose and starch synthesis. During the night, there was dominance of transcripts associated with genetic processing, such as histone regulation and RNA polymerase, ribosome and protein synthesis. Finally, the circadian clock also regulated hormone signalling pathways: a large proportion of auxin and ABA signalling components were regulated by the circadian clock in an unusual biphasic distribution. PMID:23936527

Hotta, Carlos Takeshi; Nishiyama, Milton Yutaka; Souza, Glaucia Mendes

2013-01-01

391

Single-cell resolution fluorescence imaging of circadian rhythms detected with a Nipkow spinning disk confocal system.  

PubMed

Single-point laser scanning confocal imaging produces signals with high spatial resolution in living organisms. However, photo-induced toxicity, bleaching, and focus drift remain challenges, especially when recording over several days for monitoring circadian rhythms. Bioluminescence imaging is a tool widely used for this purpose, and does not cause photo-induced difficulties. However, bioluminescence signals are dimmer than fluorescence signals, and are potentially affected by levels of cofactors, including ATP, O(2), and the substrate, luciferin. Here we describe a novel time-lapse confocal imaging technique to monitor circadian rhythms in living tissues. The imaging system comprises a multipoint scanning Nipkow spinning disk confocal unit and a high-sensitivity EM-CCD camera mounted on an inverted microscope with auto-focusing function. Brain slices of the suprachiasmatic nucleus (SCN), the central circadian clock, were prepared from transgenic mice expressing a clock gene, Period 1 (Per1), and fluorescence reporter protein (Per1::d2EGFP). The SCN slices were cut out together with membrane, flipped over, and transferred to the collagen-coated glass dishes to obtain signals with a high signal-to-noise ratio and to minimize focus drift. The imaging technique and improved culture method enabled us to monitor the circadian rhythm of Per1::d2EGFP from optically confirmed single SCN neurons without noticeable photo-induced effects or focus drift. Using recombinant adeno-associated virus carrying a genetically encoded calcium indicator, we also monitored calcium circadian rhythms at a single-cell level in a large population of SCN neurons. Thus, the Nipkow spinning disk confocal imaging system developed here facilitates long-term visualization of circadian rhythms in living cells. PMID:22480987

Enoki, Ryosuke; Ono, Daisuke; Hasan, Mazahir T; Honma, Sato; Honma, Ken-Ichi

2012-05-30

392

Circadian rhythms in diving behavior and ventilatory response to asphyxia in canvasback ducks.  

PubMed

Underwater feeding behavior was measured in 10 captive canvasback ducks (Aythya valisineria) for 12 days under a 12:12-h light-dark photoperiod. Feeding activity exhibited a daily rhythm, with 76% of dives occurring at night. In separate experiments on six of these ducks, a circadian rhythm was observed in the duration of voluntary dives. Dives at night (14.7 +/- 0.7 s) were significantly longer than those during the day (10.7 +/- 0.7 s). These day-night differences in diving behavior were accompanied by day-night differences in respiratory responses to progressive asphyxia. In the same six ducks, ventilation increased exponentially as a function of inspired CO2 concentration during rebreathing in a closed-circuit barometric plethysmograph. The exponential rate constant for inspired ventilation was significantly smaller at night (0.23 +/- 0.02) than during the day (0.26 +/- 0.01). We suggest that intermittent apneic exercise is facilitated by reduced respiratory chemosensitivity and that the respiratory and behavioral control systems are synchronized by the circadian timing system in diving ducks. PMID:9530234

Woodin, M; Stephenson, R

1998-03-01

393

Light masking of circadian rhythms of heat production, heat loss, and body temperature in squirrel monkeys  

NASA Technical Reports Server (NTRS)

Whole body heat production (HP) and heat loss (HL) were examined to determine their relative contributions to light masking of the circadian rhythm in body temperature (Tb). Squirrel monkey metabolism (n = 6) was monitored by both indirect and direct calorimetry, with telemetered measurement of body temperature and activity. Feeding was also measured. Responses to an entraining light-dark (LD) cycle (LD 12:12) and a masking LD cycle (LD 2:2) were compared. HP and HL contributed to both the daily rhythm and the masking changes in Tb. All variables showed phase-dependent masking responses. Masking transients at L or D transitions were generally greater during subjective day; however, L masking resulted in sustained elevation of Tb, HP, and HL during subjective night. Parallel, apparently compensatory, changes of HL and HP suggest action by both the circadian timing system and light masking on Tb set point. Furthermore, transient HL increases during subjective night suggest that gain change may supplement set point regulation of Tb.

Robinson, E. L.; Fuller, C. A.

1999-01-01

394

Influence of losartan intake on the circadian rhythm of melatonin secretion in humans.  

PubMed

It has been reported that losartan, an angiotensin II receptor blocker, alters the circadian rhythm of melatonin secretion and significantly reduces melatonin production. However, this finding has been confirmed at the animal experiment level only, and there are no reports of studies in humans. Therefore, we performed this study to confirm the reproducibility of the aforementioned findings of animal experiments in humans. Ten male subjects who were in good general health and free from any medical condition were recruited for this study. After a preliminary observation period of 7 days, the subjects received oral losartan treatment, 50 mg daily for 7 days. Blood samplings for measurement of the plasma melatonin concentrations were performed on day 7 of the preliminary observation period and day 7 of the losartan treatment period. The circadian rhythm of melatonin secretion after the 7-day treatment with losartan showed no significant difference from that recorded before the losartan administration. The significant decrease of the home blood pressure was observed on the afternoons. The blood samples showed significant decrease of the serum sodium and uric acid levels, along with a significant increase of the serum potassium level. The pharmacological actions of losartan at the ordinarily used clinical dose level were confirmed in humans, however, no significant inhibitory effect of the drug on melatonin secretion could be confirmed. These results are expected to be useful for guiding the proper use of angiotensin II receptor blockers. PMID:24716408

Arakawa, M; Uchida, N; Kanda, N; Kurosawa, Y; Odani, T; Kanmatsuse, K; Endo, M; Yamazaki, T; Hidaka, S

2014-03-01

395

Reproducibility of the circadian rhythms of serum cortisol and melatonin in healthy subjects: a study of three different 24-h cycles over six weeks  

Microsoft Academic Search

Plasma melatonin and cortisol are characterized by a marked circadian rhythm, but little information is available about the reproducibility and stability of these rhythms over several weeks in the same subjects. This study examined the characteristics of these rhythms in 31 healthy human subjects 20 to 30 years of age. They were synchronized with a diurnal activity from 0800 to

Brahim Selmaoui; Yvan Touitou

2003-01-01

396

Circadian Rhythm Genes CLOCK and PER3 Polymorphisms and Morning Gastric Motility in Humans  

PubMed Central

Background Clock genes regulate circadian rhythm and are involved in various physiological processes, including digestion. We therefore investigated the association between the CLOCK 3111T/C single nucleotide polymorphism and the Period3 (PER3) variable-number tandem-repeat polymorphism (either 4 or 5 repeats 54 nt in length) with morning gastric motility. Methods Lifestyle questionnaires and anthropometric measurements were performed with 173 female volunteers (mean age, 19.4 years). Gastric motility, evaluated by electrogastrography (EGG), blood pressure, and heart rate levels were measured at 8:30 a.m. after an overnight fast. For gastric motility, the spectral powers (% normal power) and dominant frequency (DF, peak of the power spectrum) of the EGG were evaluated. The CLOCK and PER3 polymorphisms were determined by polymerase chain reaction (PCR) restriction fragment length polymorphism analysis. Results Subjects with the CLOCK C allele (T/C or C/C genotypes: n = 59) showed a significantly lower DF (mean, 2.56 cpm) than those with the T/T genotype (n = 114, 2.81 cpm, P < 0.05). Subjects with the longer PER3 allele (PER34/5 or PER35/5 genotypes: n = 65) also showed a significantly lower DF (2.55 cpm) than those with the shorter PER34/4 genotype (n = 108, 2.83 cpm, P < 0.05). Furthermore, subjects with both the T/C or C/C and PER34/5 or PER35/5 genotypes showed a significantly lower DF (2.43 cpm, P < 0.05) than subjects with other combinations of the alleles (T/T and PER34/4 genotype, T/C or C/C and PER34/4 genotypes, and T/T and PER34/5 or PER35/5 genotypes). Conclusions These results suggest that minor polymorphisms of the circadian rhythm genes CLOCK and PER3 may be associated with poor morning gastric motility, and may have a combinatorial effect. The present findings may offer a new viewpoint on the role of circadian rhythm genes on the peripheral circadian systems, including the time-keeping function of the gut. PMID:25775462

Yamaguchi, Mitsue; Kotani, Kazuhiko; Tsuzaki, Kokoro; Takagi, Ayaka; Motokubota, Naoko; Komai, Naho; Sakane, Naoki; Moritani, Toshio; Nagai, Narumi

2015-01-01

397

Chronotype influences activity circadian rhythm and sleep: Differences in sleep quality between weekdays and weekend.  

PubMed

Several studies have shown the differences among chronotypes in the circadian rhythm of different physiological variables. Individuals show variation in their preference for the daily timing of activity; additionally, there is an association between chronotype and sleep duration/sleep complaints. Few studies have investigated sleep quality during the week days and weekends in relation to the circadian typology using self-assessment questionnaires or actigraphy. The purpose of this study was to use actigraphy to assess the relationship between the three chronotypes and the circadian rhythm of activity levels and to determine whether sleep parameters respond differently with respect to time (weekdays versus the weekend) in Morning-types (M-types), Neither-types (N-types) and Evening-types (E-types). The morningness-eveningness questionnaire (MEQ) was administered to 502 college students to determine their chronotypes. Fifty subjects (16?M-types, 15?N-types and 19?E-types) were recruited to undergo a 7-days monitoring period with an actigraph (Actiwacth® actometers, CNT, Cambridge, UK) to evaluate their sleep parameters and the circadian rhythm of their activity levels. To compare the amplitude and the acrophase among the three chronotypes, we used a one-way ANOVA followed by the Tukey-Kramer post-hoc test. To compare the Midline Estimating Statistic of Rhythm (MESOR) among the three chronotypes, we used a Kruskal-Wallis non-parametric test followed by pairwise comparisons that were performed using Dunn's procedure with a Bonferroni correction for multiple comparisons. The analysis of each sleep parameter was conducted using the mixed ANOVA procedure. The results showed that the chronotype was influenced by sex (?(2) with p?=?0.011) and the photoperiod at birth (?(2) with p?circadian rhythm of activity levels was influenced by the chronotype; second, the chronotype had a significant effect on sleep parameters: the E-types had a reduced sleep quality and quantity compared with the M- and N-types during weekdays, whereas the E-types reached the same levels as the other chronotypes during the weekends. These findings suggest that E-types accumulate a sleep deficit during weekdays due to social and academic commitments and that they recover from this deficit during "free days" on the weekend. PMID:25469597

Vitale, Jacopo A; Roveda, Eliana; Montaruli, Angela; Galasso, Letizia; Weydahl, Andi; Caumo, Andrea; Carandente, Franca

2015-04-01

398

Extensive and divergent circadian gene expression in liver and heart  

Microsoft Academic Search

Many mammalian peripheral tissues have circadian clocks; endogenous oscillators that generate transcriptional rhythms thought to be important for the daily timing of physiological processes. The extent of circadian gene regulation in peripheral tissues is unclear, and to what degree circadian regulation in different tissues involves common or specialized pathways is unknown. Here we report a comparative analysis of circadian gene

Kai-Florian Storch; Ovidiu Lipan; Igor Leykin; N. Viswanathan; Fred C. Davis; Wing H. Wong; Charles J. Weitz

2002-01-01

399

Circadian rhythm of natriuresis is disturbed in nondipper type of essential hypertension.  

PubMed

We examined the circadian rhythm of urinary sodium excretion and the effects of sodium restriction on rhythm in both dipper and nondipper types of essential hypertension. Patients (n = 26) with essential hypertension were maintained on relatively high- (10 to 12 g/d of sodium chloride) and low-sodium (1 to 3 g/d) diets for 1 week each. On the last day of each diet, 24-hour blood pressures (BPs) were measured every 30 minutes noninvasively with an automatic device, and on the last 3 days, urinary samples were collected for both daytime (7:00 AM to 9:30 PM) and nighttime (9:30 PM to 7:00 AM). Eight patients were classified as dippers based on a more than 10% reduction in mean arterial pressure (MAP) from daytime to nighttime on a high-sodium diet, and 18 patients were classified as nondippers. A nocturnal decrease in urinary sodium excretion rate (U(Na)V) on the high-sodium diet was observed in dippers (from 7.5 +/- 2.1 during the day to 5.3 +/- 2.5 mmol/h at night; P < 0.0001), but not in nondippers (6.7 +/- 2.1 v 7.6 +/- 2.3 mmol/h; not significant). In nondippers, the night-day ratio of sodium excretion was significantly reduced from 1.2 +/- 0.4 to 0.8 +/- 0.3 (P < 0.003) by sodium restriction; at the same time, the night-day ratio of MAP was reduced from 0.98 +/- 0.04 to 0.93 +/- 0.05 (P < 0.05). In dippers, the night-day ratios of MAP and U(Na)V were not affected by sodium restriction, and both ratios remained constant at less than 1. Before sodium restriction, the night-day ratio of sodium excretion correlated with that of MAP (r = 0.78; P < 0.0001), whereas there was no significant correlation (r = -0.05) after sodium restriction. These findings showed that the circadian rhythm of renal sodium excretion differed between the two types of essential hypertension. The enhanced nocturnal natriuresis and diminished nocturnal BP fall on a high-sodium diet, recognized in nondippers, were both normalized by sodium restriction, resulting in circadian rhythms with nocturnal dips in U(Na)V and BP. PMID:9915264

Fujii, T; Uzu, T; Nishimura, M; Takeji, M; Kuroda, S; Nakamura, S; Inenaga, T; Kimura, G

1999-01-01

400

Simulated body temperature rhythms reveal the phase-shifting behavior and plasticity of mammalian circadian oscillators  

PubMed Central

The circadian pacemaker in the suprachiasmatic nuclei (SCN) of the hypothalamus maintains phase coherence in peripheral cells through metabolic, neuronal, and humoral signaling pathways. Here, we investigated the role of daily body temperature fluctuations as possible systemic cues in the resetting of peripheral oscillators. Using precise temperature devices in conjunction with real-time monitoring of the bioluminescence produced by circadian luciferase reporter genes, we showed that simulated body temperature cycles of mice and even humans, with daily temperature differences of only 3°C and 1°C, respectively, could gradually synchronize circadian gene expression in cultured fibroblasts. The time required for establishing the new steady-state phase depended on the reporter gene, but after a few days, the expression of each gene oscillated with a precise phase relative to that of the temperature cycles. Smooth temperature oscillations with a very small amplitude could synchronize fibroblast clocks over a wide temperature range, and such temperature rhythms were also capable of entraining gene expression cycles to periods significantly longer or shorter than 24 h. As revealed by genetic loss-of-function experiments, heat-shock factor 1 (HSF1), but not HSF2, was required for the efficient synchronization of fibroblast oscillators to simulated body temperature cycles. PMID:22379191

Saini, Camille; Morf, Jörg; Stratmann, Markus; Gos, Pascal; Schibler, Ueli

2012-01-01

401

Circadian rhythm of serum cortisol in female patients with fibromyalgia syndrome.  

PubMed

Fibromyalgia syndrome (FMS) patients have disturbed sleep patterns which may lead to altered circadian rhythm in serum cortisol secretion. The aim of this study was to assess circadian changes, if any, in serum cortisol levels in female patients with FMS. Cortisol levels were estimated every 6 h during 24 h period; in 40 female patients satisfying ACR criteria for FMS (Age 36.4 ± 9.9), and 40 healthy females without FMS (Age 33.8 ± 11.1). A significant difference in the night time serum cortisol level was observed among the patients and control groups (patients, 12.9 ± 9.7 controls 5.8 ± 3.0; p < 0.01). However, no significant difference was found in serum cortisol levels in patients and control groups in the morning (patients, 28.4 ± 13.2 controls, 27.6 ± 14.5; p > 0.05), afternoon (patients, 14.4 ± 5.6 controls, 14.0 ± 6.6; p > 0.05) and evening hours (patients, 10.9 ± 5.8 controls, 8.9 ± 3.6; p > 0.05). It could be concluded that there is an abnormality in circadian secretion of cortisol in female FMS patients. PMID:24426206

Fatima, Ghizal; Das, Siddharth Kumar; Mahdi, Abbas Ali; Verma, Nar Singh; Khan, Faizan Haider; Tiwari, Amit Mani Kumar; Jafer, Tabrez; Anjum, Baby

2013-04-01

402

Focus Issue on Neuroscience: Molecular Components of Circadian Rhythms and Oscillations  

NSDL National Science Digital Library

In conjunction with this week's Neuroscience special issue of Science called Sleep, Dreams, and Memory (http://www.sciencemag.org/cgi/content/summary/294/5544/1047), the STKE presents a focus issue on Neuroscience. Organisms have circadian clocks, which cycle approximately every 24 hours and coordinate their behavior in response to environmental cues. A light-sensitive master clock is located in the suprachiasmatic nucleus of the brain, whereas clocks in the periphery of the body are thought to be set, in a light-independent manner, by signals emanating from the suprachiasmatic nucleus. Pando and Sassone-Corsi (http://stke.sciencemag.org/cgi/content/full/OC_sigtrans;2001/107/re16) review how the central and peripheral clocks might communicate and provide feedback to one another and the factors that are important for fine-tuning the oscillations of these clocks. The identity of a bona fide mammalian photoreceptor protein has remained elusive. The authors suggest that several molecules might function, singly or in concert, to perceive light cues in mammals. Circadian rhythm and the molecular mechanisms that control it have been studied in other organisms. Related material in the STKE Archives includes the Review by Woodgett (http://stke.sciencemag.org/cgi/content/full/OC_sigtrans;2001/100/re12) in which the role of glycogen synthase kinase-3 (GSK-3) in controlling circadian periodicity of the fruit fly is described as one of the biological functions of GSK-3.

John W. Nelson (the American Association for the Advancement of Science; Associate Editor for Science's STKE REV)

2001-11-06

403

Coordinated regulation of circadian rhythms and homeostasis by the suprachiasmatic nucleus  

PubMed Central

We have demonstrated that in rats activities of various enzymes related to gluconeogenesis and amino acid metabolism show circadian rhythms. Based on these results, we have explored the molecular mechanisms underlying circadian oscillation and phase response to light of the master clock located in the dorsomedial subdivision of the suprachiasmatic nucleus (SCN) and found various proteins closely related to phase response such as BIT/SHPS-1 and those of circadian oscillation, some of which are involved in protein-tyrosine phosphorylation. On the other hand, we have presented several lines of evidence that the ventrolateral subdivision of the SCN includes not only the control center of energy supply to the brain, but also that of homeostasis such as blood glucose, blood pressure, water balance, and body temperature. We have also shown that besides these functions, the latter subdivision is involved in the regulations of hormone secretions such as insulin, glucagon, corticosterone and vasopressin. It has been also shown by electrophysiological means that light exposure to rat eye enhances sympathetic nerve activity, whereas it depresses parasympathetic nerve activity. Thus, environmental light is implicated not only in the phase-shift through the retinohypthalamic tract (RHT), but also control of autonomic nerve activities through the RHT, It is also discussed in this review how the two divisions are interconnected and how environmental light is involved in this interconnection. PMID:20431263

Nakagawa, Hachiro; Okumura, Nobuaki

2010-01-01

404

Sleep and circadian rhythms in hospitalized patients with decompensated cirrhosis: effect of light therapy.  

PubMed

Patients with liver cirrhosis often exhibit sleep-wake abnormalities, which are, at least to some extent, circadian in origin. A relatively novel non-pharmacological approach to circadian disruption is appropriately timed bright light therapy. The aims of this pilot study were to investigate sleep-wake characteristics of a well-characterized population of inpatients with cirrhosis, and to evaluate the efficacy of bright light therapy in the hospital setting. Twelve consecutive inpatients with cirrhosis underwent complete sleep-wake assessment, to include qualitative and semi-quantitative (actigraphic) indices of night-time sleep quality, daytime sleepiness, diurnal preference, habitual sleep timing, quality of life, mood and circadian rhythmicity [i.e. urine collections for measurement of the melatonin metabolite 6-sulphatoxymelatonin (aMT6s)]. Patients showed extremely impaired night sleep quality (Pittsburg Sleep Quality Index global score: 16.3 ± 2.1) and daytime sleepiness was common (Epworth Sleepiness Scale: 8.3 ± 3.2). Five patients were randomly assigned to a single room in which lighting was controlled in relation to timing, spectral composition and intensity (lights on at 06:30 and off at 22:30, blue-enriched, more intense light in the morning, red-enriched, less intense light in the afternoon/evening); the others stayed in identical rooms with standard lighting. Sleep diaries revealed poor sleep quality, prolonged sleep latency (67 ± 138 min) and a reduced sleep efficiency (69 ± 21 %). These features were confirmed by actigraphy (sleep efficiency: 71 ± 13 %; fragmentation index: 55 ± 15 %). Quality of life was globally impaired, and mood moderately depressed (Beck Depression Inventory: 19.4 ± 7.9). Seven patients underwent serial urine collections: no circadian aMT6s rhythm was detected in any of them, neither at baseline, nor during the course of hospitalization in either room (n = 4). In conclusion, sleep and circadian rhythms in hospitalized, decompensated patients with cirrhosis are extremely compromised. Treatment with bright light therapy did not show obvious, beneficial effects, most likely in relation to the severity of disturbance at baseline. PMID:25135598

De Rui, M; Middleton, B; Sticca, A; Gatta, A; Amodio, P; Skene, D J; Montagnese, S

2015-02-01

405

Dening the role of Drosophila lateral neurons in the control of circadian activity and eclosion rhythms by  

E-print Network

& Kay, 2000). In both cases, a brain-located circadian pacemaker is responsible for the control that the activity pacemaker stems from a limited number of neurons, in the accessory medulla of the optic lobe and functional organ- ization of the pacemaker that controls activity rhythms. The expression of period (per

Rouyer, Francois

406

Brain Research, 302(1984)371-377 371 A Retinohypothalamic Pathway in Man: Light Mediation of Circadian Rhythms  

E-print Network

Brain Research, 302(1984)371-377 371 Elsevier BRE 10073 A Retinohypothalamic Pathway in Man: Light: suprachiasmatic nucleus -- retinohypothalamic pathway -- human hypothalamus -- circadian rhythms -- diurnal cycles - - paraphenylenediamine It has been proposed that, in animals, a retinohypothalamic pathway exists which mediates

Schaechter, Judith D.

407

Chronotype differences in circadian rhythms of temperature, melatonin, and sleepiness as measured in a modified constant routine protocol  

PubMed Central

Evening chronotypes typically have sleep patterns timed 2–3 hours later than morning chronotypes. Ambulatory studies have suggested that differences in the timing of underlying circadian rhythms as a cause of the sleep period differences. However, differences in endogenous circadian rhythms are best explored in laboratory protocols such as the constant routine. We used a 27-hour modified constant routine to measure the endogenous core temperature and melatonin circadian rhythms as well as subjective and objective sleepiness from hourly 15-minute sleep opportunities. Ten (8f) morning type individuals were compared with 12 (8f) evening types. All were young, healthy, good sleepers. The typical sleep onset, arising times, circadian phase markers for temperature and melatonin and objective sleepiness were all 2–3 hours later for the evening types than morning types. However, consistent with past studies the differences for the subjective sleepiness rhythms were much greater (5–9 hours). Therefore, the present study supports the important role of subjective alertness/sleepiness in determining the sleep period differences between morning and evening types and the possible vulnerability of evening types to delayed sleep phase disorder. PMID:23616692

Lack, Leon; Bailey, Michelle; Lovato, Nicole; Wright, Helen

2009-01-01

408

Circadian Rhythms in Executive Function during the Transition to Adolescence: The Effect of Synchrony between Chronotype and Time of Day  

ERIC Educational Resources Information Center

To explore the influence of circadian rhythms on executive function during early adolescence, we administered a battery of executive function measures (including a Go-Nogo task, the Iowa Gambling Task, a Self-ordered Pointing task, and an Intra/Extradimensional Shift task) to Morning-preference and Evening-preference participants (N = 80) between…

Hahn, Constanze; Cowell, Jason M.; Wiprzycka, Ursula J.; Goldstein, David; Ralph, Martin; Hasher, Lynn; Zelazo, Philip David

2012-01-01

409

Stochastic models of cellular circadian rhythms in plants help to understand the impact of noise on robustness and clock structure  

PubMed Central

Rhythmic behavior is essential for plants; for example, daily (circadian) rhythms control photosynthesis and seasonal rhythms regulate their life cycle. The core of the circadian clock is a genetic network that coordinates the expression of specific clock genes in a circadian rhythm reflecting the 24-h day/night cycle. Circadian clocks exhibit stochastic noise due to the low copy numbers of clock genes and the consequent cell-to-cell variation: this intrinsic noise plays a major role in circadian clocks by inducing more robust oscillatory behavior. Another source of noise is the environment, which causes variation in temperature and light intensity: this extrinsic noise is part of the requirement for the structural complexity of clock networks. Advances in experimental techniques now permit single-cell measurements and the development of single-cell models. Here we present some modeling studies showing the importance of considering both types of noise in understanding how plants adapt to regular and irregular light variations. Stochastic models have proven useful for understanding the effect of regular variations. By contrast, the impact of irregular variations and the interaction of different noise sources are less well studied. PMID:25374576

Guerriero, Maria L.; Akman, Ozgur E.; van Ooijen, Gerben

2014-01-01

410

The expression of a circadian rhythm in two strains of Chlamydomonas reinhardii in space  

NASA Astrophysics Data System (ADS)

During the D1 mission the endogenous circadian rhythm of the photoaccumulation response persisted in two strains of Chlamydomonas. The amplitude was about twice as high in space as on the ground indicating that a larger fractionof cells was able to contribute to the expression of the rhythm. On the ground, cells usually enter the light cone of the illuminated area in the recording cuvette on the upper edge and leave it, due to gravity, on the lower one in a pulsating manner. This sometimes produces high frequency oscillations of light extinction on the ground. In space there were no such fluctuations; instead, cells swam into the light and stayed there harvesting more light energy for photosynthesis than did control cells. This probably enhanced the survival rate and increased the fraction of motile cells which contribute to the photoaccumulation. A more sophisticated evaluation technique allowed determination of the phase in the short period strain; it was delayed by two hours compared to the control. In an acetate free wildtype sample a rhythm with a period of about 24 hours was also detected.

Mergenhagen, Dieter; Mergenhagen, Elke

411

Dopamine receptor 1 neurons in the dorsal striatum regulate food anticipatory circadian activity rhythms in mice  

PubMed Central

Daily rhythms of food anticipatory activity (FAA) are regulated independently of the suprachiasmatic nucleus, which mediates entrainment of rhythms to light, but the neural circuits that establish FAA remain elusive. In this study, we show that mice lacking the dopamine D1 receptor (D1R KO mice) manifest greatly reduced FAA, whereas mice lacking the dopamine D2 receptor have normal FAA. To determine where dopamine exerts its effect, we limited expression of dopamine signaling to the dorsal striatum of dopamine-deficient mice; these mice developed FAA. Within the dorsal striatum, the daily rhythm of clock gene period2 expression was markedly suppressed in D1R KO mice. Pharmacological activation of D1R at the same time daily was sufficient to establish anticipatory activity in wild-type mice. These results demonstrate that dopamine signaling to D1R-expressing neurons in the dorsal striatum plays an important role in manifestation of FAA, possibly by synchronizing circadian oscillators that modulate motivational processes and behavioral output. DOI: http://dx.doi.org/10.7554/eLife.03781.001 PMID:25217530

Gallardo, Christian M; Darvas, Martin; Oviatt, Mia; Chang, Chris H; Michalik, Mateusz; Huddy, Timothy F; Meyer, Emily E; Shuster, Scott A; Aguayo, Antonio; Hill, Elizabeth M; Kiani, Karun; Ikpeazu, Jonathan; Martinez, Johan S; Purpura, Mari; Smit, Andrea N; Patton, Danica F; Mistlberger, Ralph E; Palmiter, Richard D; Steele, Andrew D

2014-01-01

412

Adjustment of sleep and the circadian temperature rhythm after flights across nine time zones  

NASA Technical Reports Server (NTRS)

The adjustment of sleep-wake patterns and the circadian temperature rhythm was monitored in nine Royal Norwegian Airforce volunteers operating P-3 aircraft during a westward training deployment across nine time zones. Subjects recorded all sleep and nap times, rated nightly sleep quality, and completed personality inventories. Rectal temperature, heart rate, and wrist activity were continuously monitored. Adjustment was slower after the return eastward flight than after the outbound westward flight. The eastward flight produced slower readjustment of sleep timing to local time and greater interindividual variability in the patterns of adjustment of sleep and temperature. One subject apparently exhibited resynchronization by partition, with the temperature rhythm undergoing the reciprocal 15-h delay. In contrast, average heart rates during sleep were significantly elevated only after westward flight. Interindividual differences in adjustment of the temperature rhythm were correlated with some of the personality measures. Larger phase delays in the overall temperature waveform (as measured on the 5th day after westward flight) were exhibited by extraverts, and less consistently by evening types.

Gander, Philippa H.; Myhre, Grete; Graeber, R. Curtis; Lauber, John K.; Andersen, Harald T.

1989-01-01

413

Influence of sleep-wake and circadian rhythm disturbances in psychiatric disorders  

PubMed Central

Recent evidence shows that the temporal alignment between the sleep-wake cycle and the circadian pacemaker affects self-assessment of mood in healthy subjects. Despite the differences in affective state between healthy subjects and patients with psychiatric disorders, these results have implications for analyzing diurnal variation of mood in unipolar and bipolar affective disorders and sleep disturbances in other major psychiatric conditions such as chronic schizophrenia. In a good proportion of patients with depression, mood often improves over the course of the day; an extension of waking often has an antidepressant effect. Sleep deprivation has been described as a treatment for depression for more than 30 years, and approximately 50% to 60% of patients with depression respond to this approach, especially those patients who report that their mood improves over the course of the day. The mechanisms by which sleep deprivation exerts its antidepressant effects are still controversial, but a reduction in rapid eye movement sleep (REM sleep), sleep pressure and slow-wave sleep (SWS), or a circadian phase disturbance, have been proposed. Although several studies support each of these hypotheses, none is sufficient to explain all observations reported to date. Unfortunately, the disturbed sleep-wake cycle or behavioural activities of depressed patients often explain several of the abnormalities reported in the diurnal rhythms of these patients. Thus, protocols that specifically manipulate the sleep-wake cycle to unmask the expression of the endogenous circadian pacemaker are greatly needed. In chronic schizophrenia, significant disturbances in sleep continuity, REM sleep, and SWS have been consistently reported. These disturbances are different from those observed in depression, especially with regard to REM sleep. Circadian phase abnormalities in schizophrenic patients have also been reported. Future research is expected to clarify the nature of these abnormalities. Images Fig. 1 PMID:11109296

Boivin, DB

2000-01-01

414

Hepatitis B virus X protein disrupts the balance of the expression of circadian rhythm genes in hepatocellular carcinoma  

PubMed Central

The human circadian rhythm is controlled by at least eight circadian clock genes and disruption of the circadian rhythm is associated with cancer development. The present study aims to elucidate the association between the expression of circadian clock genes and the development of hepatocellular carcinoma (HCC), and also to reveal whether the hepatitis B virus X protein (HBx) is the major regulator that contributes to the disturbance of circadian clock gene expression. The mRNA levels of circadian clock genes in 30 HCC and the paired peritumoral tissues were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A stable HBx-expressing cell line, Bel-7404-HBx, was established through transfection of HBx plasmids. The mRNA level of circadian clock genes was also detected by RT-qPCR in these cells. Compared with the paired peritumoral tissues, the mRNA levels of the Per1, Per2, Per3 and Cry2 genes in HCC tissue were significantly lower (P<0.05), while no significant difference was observed in the expression levels of CLOCK, BMAL1, Cry1 and casein kinase 1? (CK1?; P>0.05). Compared with Bel-7404 cells, the mRNA levels of the CLOCK, Per1 and Per2 genes in Bel-7404-HBx cells were significantly increased, while the mRNA levels of the BMAL1, Per3, Cry1, Cry2 and CKI? genes were decreased (P<0.05). Thus, the present study identified that disturbance of the expression of circadian clock genes is common in HCC. HBx disrupts the expression of circadian clock genes and may, therefore, induce the development of HCC. PMID:25360177

YANG, SHENG-LI; YU, CHAO; JIANG, JIAN-XIN; LIU, LI-PING; FANG, XIEFAN; WU, CHAO

2014-01-01

415

Effects of Exposure to Intermittent versus Continuous Red Light on Human Circadian Rhythms, Melatonin Suppression, and Pupillary Constriction  

PubMed Central

Exposure to light is a major determinant of sleep timing and hormonal rhythms. The role of retinal cones in regulating circadian physiology remains unclear, however, as most studies have used light exposures that also activate the photopigment melanopsin. Here, we tested the hypothesis that exposure to alternating red light and darkness can enhance circadian resetting responses in humans by repeatedly activating cone photoreceptors. In a between-subjects study, healthy volunteers (n?=?24, 21–28 yr) lived individually in a laboratory for 6 consecutive days. Circadian rhythms of melatonin, cortisol, body temperature, and heart rate were assessed before and after exposure to 6 h of continuous red light (631 nm, 13 log photons cm?2 s?1), intermittent red light (1 min on/off), or bright white light (2,500 lux) near the onset of nocturnal melatonin secretion (n?=?8 in each group). Melatonin suppression and pupillary constriction were also assessed during light exposure. We found that circadian resetting responses were similar for exposure to continuous versus intermittent red light (P?=?0.69), with an average phase delay shift of almost an hour. Surprisingly, 2 subjects who were exposed to red light exhibited circadian responses similar in magnitude to those who were exposed to bright white light. Red light also elicited prolonged pupillary constriction, but did not suppress melatonin levels. These findings suggest that, for red light stimuli outside the range of sensitivity for melanopsin, cone photoreceptors can mediate circadian phase resetting of physiologic rhythms in some individuals. Our results also show that sensitivity thresholds differ across non-visual light responses, suggesting that cones may contribute differentially to circadian resetting, melatonin suppression, and the pupillary light reflex during exposure to continuous light. PMID:24797245

Ho Mien, Ivan; Chua, Eric Chern-Pin; Lau, Pauline; Tan, Luuan-Chin; Lee, Ivan Tian-Guang; Yeo, Sing-Chen; Tan, Sara Shuhui; Gooley, Joshua J.

2014-01-01

416

Respiratory rhythms generated in the lamprey rhombencephalon.  

PubMed

Brainstem networks generating the respiratory rhythm in lampreys are still not fully characterized. In this study, we described the patterns of respiratory activities and we identified the general location of underlying neural networks. In a semi-intact preparation including the brain and gills, rhythmic discharges were recorded bilaterally with surface electrodes placed over the vagal motoneurons. The main respiratory output driving rhythmic gill movements consisted of short bursts (40.9+/-15.6 ms) of discharge occurring at a frequency of 1.0+/-0.3 Hz. This fast pattern was interrupted by long bursts (506.3+/-174.6 ms) recurring with an average period of 37.4+/-24.9 s. After isolating the brainstem by cutting all cranial nerves, the frequency of the short respiratory bursts did not change significantly, but the slow pattern was less frequent. Local injections of a glutamate agonist (AMPA) and antagonists (6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) or D,L-amino-5-phosphonopentanoic acid (AP5)) were made over different brainstem regions to influence respiratory output. The results were similar in the semi-intact and isolated-brainstem preparations. Unilateral injection of AP5 or CNQX over a rostral rhombencephalic region, lateral to the rostral pole of the trigeminal motor nucleus, decreased the frequency of the fast respiratory rhythm bilaterally or stopped it altogether. Injection of AMPA at the same site increased the rate of the fast respiratory rhythm and decreased the frequency of the slow pattern. The activity recorded in this area was synchronous with that recorded over the vagal motoneurons. After a complete transverse lesion of the brainstem caudal to the trigeminal motor nucleus, the fast rhythm was confined to the rostral area, while only the slow activity persisted in the vagal motoneurons. Our results support the hypothesis that normal breathing depends on the activity of neurons located in the rostral rhombencephalon in lampreys, whereas the caudal rhombencephalon generates the slow pattern. PMID:17618060

Martel, B; Guimond, J C; Gariépy, J F; Gravel, J; Auclair, F; Kolta, A; Lund, J P; Dubuc, R

2007-08-10

417

Embryonic emergence of the respiratory rhythm generator.  

PubMed

Breathing is vital for life ex utero and therefore requires that the respiratory rhythm generator (RRG), the central neural network generating the continuous rhythmic motor command, be functional at birth. The RRG, located in the brainstem, appears to comprise two interacting respiratory oscillators: the parafacial respiratory group (pFRG), and the preBötzinger complex (preBötC). Data on the establishment of these respiratory oscillators during embryonic and foetal periods are beginning to be produced. The present paper provides a short review of the current knowledge regarding: (i) the emergence of activity in the two respiratory oscillators and (ii) their functional coupling during prenatal development in rodents. PMID:19560563

Fortin, Gilles; Thoby-Brisson, Muriel

2009-08-31

418

Effects of altitude on circadian rhythm of adult locomotor activity in Himalayan strains of Drosophila helvetica  

PubMed Central

Background We recently reported that the altitude of origin altered the photic and thermal sensitivity of the circadian pacemaker controlling eclosion and oviposition rhythms of high altitude Himalayan strains of Drosophila ananassae. The present study was aimed at investigating the effects of altitude of origin on the pacemaker controlling the adult locomotor activity rhythm of D. helvetica. Methods Locomotor activity rhythms of the high altitude Himalayan (haH) strain (Hemkund-Sahib, 4,121 m above sea level) and the low altitude Himalayan (laH) strain (Birahi, 1,132 m a.s.l.) of D. helvetica were assayed by two experiments. The first experiment examined the natural entrainment pattern in light-dark (LD) cycles at the breeding site of each strain. The second experiment examined the entrainment parameters in LD 12:12 cycles and the period of free-running rhythm in constant darkness (DD) under controlled laboratory conditions. Results When entrained by natural or artificial LD cycles, the haH strain had an unimodal activity pattern with a single peak that commenced in the forenoon and continued till evening, while the laH strain had a bimodal activity pattern in which the morning peak occurred before lights-on and was separated by about 4 h from the evening peak. Unimodality of the haH strain was retained in DD; however, bimodality of the laH strain was abolished in DD since the evening peak disappeared immediately after the trasfer from LD 12:12 to DD. The period of the free-running rhythm of the haH strain was ~26.1 h, whereas that of the laH strain was ~21.7 h. Conclusion Parameters of entrainment and free-running rhythm of the adult locomotor activity of the haH strain of D. helvetica were strikingly different from those of the laH strain and were likely due to ecological adaptations to the prevailing environmental conditions at the altitude where the species evolved. PMID:17210086

Vanlalhriatpuia, Keny; Chhakchhuak, Vanlalnghaka; Moses, Satralkar K; Iyyer, SB; Kasture, MS; Shivagaje, AJ; Rajneesh, Barnabas J; Joshi, Dilip S

2007-01-01

419

The effects of feedback lighting on the circadian drinking rhythm in the diurnal new world primate Saimiri sciureus  

NASA Technical Reports Server (NTRS)

Feedback lighting provides illumination primarily during the subjective night (i.e., the photosensitive portion of the circadian cycle) in response to a given behavior. This technique has previously been used to test the nonparametric model of entrainment in nocturnal rodents. In three species (Rattus norvegicus, Mesocricetus auratus, and Mus musculus), the free-running period of the locomotor activity rhythm was similar whether the animals were exposed to continuous light or discrete light pulses occurring essentially only during the subjective night (i.e., feedback lighting). In the current experiments, feedback lighting was presented to squirrel monkeys so that light fell predominantly during the subjective night. Feedback lighting was linked to the drinking behavior in this diurnal primate so that when the animal drank, the lights went out. Despite the seemingly adverse predicament, the monkeys maintained regular circadian drinking rhythms. Furthermore, just as the period of the free-running activity rhythms of nocturnal rodents exposed to continuous light or feedback lighting were similar, the period of the drinking rhythms of the squirrel monkeys in continuous light and feedback lighting were comparable (25.6 +/- 0.1 and 25.9 +/- 0.1 hours, respectively), despite a substantial decrease in the total amount of light exposure associated with feedback lighting. The free-running period of monkeys exposed to continuous dark (24.5 +/- 0.1 hours) was significantly shorter than either of the two lighting conditions (P < 0.001). The results presented for the drinking rhythm were confirmed by examination of the temperature and activity rhythms. Therefore, discrete light pulses given predominately during the subjective night are capable of simulating the effects of continuous light on the free-running period of the circadian rhythms of a diurnal primate. The response of squirrel monkeys to feedback lighting thus lends further support for the model and suggests that the major entrainment mechanisms are similar in nocturnal rodents and diurnal primates.

Ferraro, J. S.; Sulzman, F. M.

1988-01-01

420

A Circadian Clock in Antarctic Krill: An Endogenous Timing System Governs Metabolic Output Rhythms in the Euphausid Species Euphausia superba  

PubMed Central

Antarctic krill, Euphausia superba, shapes the structure of the Southern Ocean ecosystem. Its central position in the food web, the ongoing environmental changes due to climatic warming, and increasing commercial interest on this species emphasize the urgency of understanding the adaptability of krill to its environment. Krill has evolved rhythmic physiological and behavioral functions which are synchronized with the daily and seasonal cycles of the complex Southern Ocean ecosystem. The mechanisms, however, leading to these rhythms are essentially unknown. Here, we show that krill possesses an endogenous circadian clock that governs metabolic and physiological output rhythms. We found that expression of the canonical clock gene cry2 was highly rhythmic both in a light-dark cycle and in constant darkness. We detected a remarkable short circadian period, which we interpret as a special feature of the krill's circadian clock that helps to entrain the circadian system to the extreme range of photoperiods krill is exposed to throughout the year. Furthermore, we found that important key metabolic enzymes of krill showed bimodal circadian oscillations (?9–12 h period) in transcript abundance and enzymatic activity. Oxygen consumption of krill showed ?9–12 h oscillations that correlated with the temporal activity profile of key enzymes of aerobic energy metabolism. Our r