37 results on '"Ultradian rhythms"'
Search Results
2. Free‐running circadian period in adolescents and adults.
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Crowley, Stephanie J. and Eastman, Charmane I.
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CIRCADIAN rhythms , *BIOLOGICAL rhythms , *ULTRADIAN rhythms , *MELATONIN , *TEENAGERS - Abstract
Summary: Sleep timing shifts later during adolescence (second decade). This trend reverses at ~20 years and continues to shift earlier into adulthood. The current analysis examined the hypothesis that a longer free‐running circadian period during late adolescence (14–17 years) compared with adulthood (30–45 years) accounts for sleep timing differences. Sex and ancestry were also examined because previous reports find that women and those with African‐American ancestry have shorter free‐running periods. Circadian period was measured using an ultradian dark–light protocol (2 hr dark/sleep, 2 hr dim room light [~20 lux]/wake) over 3.4 days. Dim light melatonin onsets were measured before and after the ultradian protocol, from which the circadian period was derived. In contrast to our hypothesis, we found that free‐running circadian period was similar in adolescents and adults. African‐American adults had shorter free‐running circadian periods compared with adults of other ancestries. This ancestry difference was not seen in the adolescent group. Finally, we observed a non‐significant trend for shorter free‐running circadian periods in females compared with males. These data suggest that age‐related changes in circadian period after late adolescence do not account for sleep timing differences. These data provide further support for ancestry‐related differences in period, particularly in adults. Whether the large difference in circadian period between African‐American and other ancestries emerges later in development should be explored. [ABSTRACT FROM AUTHOR]
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- 2018
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3. Circadian and ultradian patterns of epileptiform discharges differ by seizure-onset location during long-term ambulatory intracranial monitoring.
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Spencer, David C., Sun, Felice T., Brown, Sarah N., Jobst, Barbara C., Fountain, Nathan B., Wong, Victoria S. S., Mirro, Emily A., and Quigg, Mark
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EPILEPSY , *CIRCADIAN rhythms , *ULTRADIAN rhythms , *SPASMS , *PEOPLE with epilepsy - Abstract
Objective Previous studies reporting circadian patterns of epileptiform activity and seizures are limited by (1) short-term recording in an epilepsy monitoring unit (EMU) with altered antiepileptic drugs (AEDs) and sleep, or (2) subjective seizure diary reports. We studied circadian patterns using long-term ambulatory intracranial recordings captured by the NeuroPace RNS System. Methods Retrospective study of RNS System trial participants with stable detection parameters over a continuous 84-day period. We analyzed all detections and long device-detected epileptiform events (long episodes) and defined a subset of subjects in whom long episodes represented electrographic seizures (LE-SZ). Spectrum resampling determined the dominant frequency periodicity and cosinor analysis identified significant circadian peaks in detected activity. Chi-square analysis was used to compare subjects grouped by region of seizure onset. Results In the 134 subjects, detections showed a strongly circadian and uniform pattern irrespective of region of onset that peaked during normal sleep hours. In contrast, long episodes and LE-SZ patterns varied by region. Neocortical regions had a monophasic, nocturnally dominant rhythm, whereas limbic regions showed a more complex pattern and diurnal peak. Rhythms in some individual limbic subjects were best fit by a dual oscillator (circadian + ultradian) model. Significance Epileptiform activity has a strong 24 h periodicity with peak nocturnal occurrence. Limbic and neocortical epilepsy show divergent circadian influences. These findings confirm that circadian patterns of epileptiform activity vary by seizure-onset zone, with implications for treatment and safety, including SUDEP. [ABSTRACT FROM AUTHOR]
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- 2016
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4. Secretory pattern and regulatory mechanism of growth hormone in cattle.
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Kasuya, Etsuko
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SOMATOTROPIN , *SECRETION , *ULTRADIAN rhythms , *ANIMAL species , *HYPOTHALAMUS - Abstract
The ultradian rhythm of growth hormone (GH) secretion has been known in several animal species for years and has recently been observed in cattle. Although the physiological significance of the rhythm is not yet fully understood, it appears essential for normal growth. In this review, previous studies concerning the GH secretory pattern in cattle, including its ultradian rhythm, are introduced and the regulatory mechanism is discussed on the basis of recent findings. [ABSTRACT FROM AUTHOR]
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- 2016
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5. Assessing cell cycle-based methods of measuring Prochlorococcus division rates using an individual-based model.
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Hynes, Annette M., Rhodes, Kirsten L., and Binder, Brian J.
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PROCHLOROCOCCUS ,CELL division ,CELL cycle ,FLOW cytometry ,ULTRADIAN rhythms ,BACTERIA - Abstract
The picocyanobacterium Prochlorococcus is a major contributor to primary production in tropical and temperate oceans. Division rates Qipop) of Prochlorococcus populations can be calculated by following their partially synchronized cell cycles, but one major source of error in these calculations is the estimation of the duration of the S and G2 phases, T
SG2 . Here we have used data generated by an individual-based model (IBM) of the Prochlorococcus cell cycle to analyze an array of estimation methods and range of sample intervals to determine the best way to calculate µpop from time course data. Among the traditional methods using the cell cycle approach, areal median gave the best estimate of µpop ; optimizing the IBM itself gave the best estimate overall. A size-based matrix model also gave reasonable results, except at ultradian growth rates. These methods were applied to a time series in the Sargasso Sea to measure Prochlorococcus µpop in situ. The IBM was an effective test bed to investigate division rate estimates and provide recommendations for applying these estimates to field populations. [ABSTRACT FROM AUTHOR]- Published
- 2015
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6. Subcutaneous pulsatile glucocorticoid replacement therapy.
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Russell, Georgina M., Durant, Claire, Ataya, Alia, Papastathi, Chrysoula, Bhake, Ragini, Woltersdorf, Wolfram, and Lightman, Stafford
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SUBCUTANEOUS infusions , *GLUCOCORTICOIDS , *ULTRADIAN rhythms , *CIRCADIAN rhythms , *PULSE (Heart beat) - Abstract
The glucocorticoid hormone cortisol is released in pulses resulting in a complex and dynamic ultradian rhythm of plasma cortisol that underlies the classical circadian rhythm. These oscillating levels are also seen at the level of tissues such as the brain and trigger pulses of gene activation and downstream signalling. Different patterns of glucocorticoid presentation (constant vs pulsatile) result not only in different patterns of gene regulation but also in different neuroendocrine and behavioural responses. Current 'optimal' glucocorticoid replacement therapy results in smooth hormone blood levels and does not replicate physiological pulsatile cortisol secretion. Validation of a novel portable pulsatile continuous subcutaneous delivery system in healthy volunteers under dexamethasone and metyrapone suppression. Pulsatile subcutaneous hydrocortisone more closely replicates physiological circadian and ultradian rhythmicity. [ABSTRACT FROM AUTHOR]
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- 2014
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7. The endogenous circadian temperature period length (tau) in delayed sleep phase disorder compared to good sleepers.
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Micic, Gorica, Bruyn, Amanda, Lovato, Nicole, Wright, Helen, Gradisar, Michael, Ferguson, Sally, Burgess, Helen J., and Lack, Leon
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ATTENTION-deficit hyperactivity disorder , *CIRCADIAN rhythms , *MEDICAL thermometry , *SLEEP disorders treatment , *INSOMNIA , *ULTRADIAN rhythms - Abstract
The currently assumed aetiology for delayed sleep phase disorder ( DSPD) is a delay of the circadian system. Clinicians have sought to use bright light therapy, exogenous melatonin or chronotherapy to correct the disorder. However, these treatments have achieved unreliable outcomes for DSPD patients and, as such, one suggestion has been that the disorder may be caused by a longer than normal circadian rhythm period length (i.e. tau). The present study investigated this premise using a 78-h ultradian, ultra-short sleep-wake cycle. This constant bedrest routine was used to simulate a series of 1-h long 'days' by alternating 20-min sleep opportunities and 40 min of enforced wakefulness. Thirteen participants were recruited for the study including, six people diagnosed with DSPD according to the International Classification of Sleep Disorders-2 [mean age = 22.0, standard deviation ( SD) = 3.3] and seven good sleepers (mean age = 23.1, SD = 3.9) with normal sleep timing. The DSPD participants' core temperature rhythm tau (mean = 24 h 54 min, SD = 23 min) was significantly longer ( t = −2.33, P = 0.04, Cohen's d = 1.91) than the good sleepers' (mean 24 h 29 min, SD = 16 min). The temperature rhythm of the DSPD participants delayed more rapidly (i.e. >25 min day−1) than the good sleepers'. These findings provide an explanation for the difficulty that DSPD patients have in phase advancing to a more conventional sleep time and their frequent relapse following treatment. The outcomes of this study support a vigorous and continued application of chronobiological and behavioural therapies to entrain DSPD patients to their desired earlier sleep times. [ABSTRACT FROM AUTHOR]
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- 2013
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8. Ultradian corticosterone secretion is maintained in the absence of circadian cues.
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Waite, Eleanor J., McKenna, Mervyn, Kershaw, Yvonne, Walker, Jamie J., Cho, Kwangwook, Piggins, Hugh D., and Lightman, Stafford L.
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CORTICOSTERONE , *SUPRACHIASMATIC nucleus , *ULTRADIAN rhythms , *CIRCADIAN rhythms , *HYPOTHALAMIC-pituitary-adrenal axis , *LABORATORY rats , *SECRETION - Abstract
Plasma levels of corticosterone exhibit both circadian and ultradian rhythms. The circadian component of these rhythms is regulated by the suprachiasmatic nucleus (SCN). Our studies investigate the importance of the SCN in regulating ultradian rhythmicity. Two approaches were used to dissociate the hypothalamic-pituitary-adrenal (HPA) axis from normal circadian input in rats: (i) exposure to a constant light (LL) environment and (ii) electrolytic lesioning of the SCN. Blood was sampled using an automated sampling system. As expected, both treatments resulted in a loss of the circadian pattern of corticosterone secretion. Ultradian pulsatile secretion of corticosterone however, was maintained across the 24 h in all animals. Furthermore, the loss of SCN input revealed an underlying relationship between locomotor and HPA activity. In control (LD) rats there was no clear correlation between ultradian locomotor activity and hormone secretion, whereas, in LL rats, episodes of ultradian activity were consistently followed by periods of increased pulsatile hormone secretion. These data clearly demonstrate that the ultradian rhythm of corticosterone secretion is generated through a mechanism independent of the SCN input, supporting recent evidence for a sub-hypothalamic pulse generator. [ABSTRACT FROM AUTHOR]
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- 2012
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9. Ultradian rhythm in the intestine of Caenorhabditis elegans is controlled by the C-terminal region of the FLR-1 ion channel and the hydrophobic domain of the FLR-4 protein kinase.
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Kobayashi, Yuri, Kimura, Koutarou D., and Katsura, Isao
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ULTRADIAN rhythms , *CAENORHABDITIS elegans , *DEFECATION , *PROTEIN kinases , *ION channels , *EPITHELIAL cells , *SODIUM channels , *BEHAVIOR - Abstract
Defecation behavior in Caenorhabditis elegans is driven by an endogenous ultradian clock in the intestine. Its periods are positively regulated by FLR-1, an ion channel of the epithelial sodium channel/degenerin superfamily, and FLR-4, a protein kinase with a hydrophobic domain at the carboxyl terminus. FLR-1 has many putative phosphorylation sites in the C-terminal intracellular region. This structure implies that the periods may be regulated by the phosphorylation of FLR-1 by FLR-4, but it remains to be clarified. Here, we show that a truncated FLR-1 lacking the C-terminal intracellular region resulted in longer periods, suggesting that this region is involved in the negative regulation of defecation cycle periods. Contrary to our expectation, FLR-4 was still necessary for the function of the truncated FLR-1. Furthermore, FLR-4 containing a kinase-dead mutation or lacking the whole kinase domain was sufficient for normal defecation cycle periods. FLR-4 was necessary for the stable expression of FLR-1::GFP, and its hydrophobic domain was sufficient also for this function. FLR-1 and FLR-4 are often colocalized in the plasma membrane. These data showed an unexpected role of FLR-4: its hydrophobic domain stabilizes the FLR-1 ion channel, a key regulator of defecation cycle periods in the intestine. [ABSTRACT FROM AUTHOR]
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- 2011
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10. Encoding and Decoding Mechanisms of Pulsatile Hormone Secretion.
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Walker, J. J., Terry, J. R., Tsaneva-Atanasova, K., Armstrong, S. P., McArdle, C. A., and Lightman, S. L.
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HORMONES , *ENDOCRINE system , *GONADOTROPIN , *GLUCOCORTICOIDS , *MATHEMATICAL models , *ULTRADIAN rhythms , *NEUROENDOCRINOLOGY , *HYPOTHALAMIC-pituitary-adrenal axis - Abstract
Ultradian pulsatile hormone secretion underlies the activity of most neuroendocrine systems, including the hypothalamic-pituitary adrenal (HPA) and gonadal (HPG) axes, and this pulsatile mode of signalling permits the encoding of information through both amplitude and frequency modulation. In the HPA axis, glucocorticoid pulse amplitude increases in anticipation of waking, and, in the HPG axis, changing gonadotrophin-releasing hormone pulse frequency is the primary means by which the body alters its reproductive status during development (i.e. puberty). The prevalence of hormone pulsatility raises two crucial questions: how are ultradian pulses encoded (or generated) by these systems, and how are these pulses decoded (or interpreted) at their target sites? We have looked at mechanisms within the HPA axis responsible for encoding the pulsatile mode of glucocorticoid signalling that we observe in vivo. We review evidence regarding the 'hypothalamic pulse generator' hypothesis, and describe an alternative model for pulse generation, which involves steroid feedback-dependent endogenous rhythmic activity throughout the HPA axis. We consider the decoding of hormone pulsatility by taking the HPG axis as a model system and focussing on molecular mechanisms of frequency decoding by pituitary gonadotrophs. [ABSTRACT FROM AUTHOR]
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- 2010
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11. Glucocorticoid Ultradian Rhythmicity Directs Cyclical Gene Pulsing of the Clock Gene Period 1 in Rat Hippocampus.
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Conway-Campbell, B. L ., Sarabdjitsingh, R. A., McKenna, M. A., Pooley, J. R., Kershaw, Y. M., Meijer, O. C., de Kloet, E. R., and Lightman, S. L .
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GLUCOCORTICOID receptors , *ULTRADIAN rhythms , *HIPPOCAMPUS (Brain) , *LEARNING in animals , *CORTICOSTERONE , *OLIGONUCLEOTIDES , *CONFOCAL microscopy , *RATS - Abstract
In vivo glucocorticoid (GC) secretion exhibits a distinctive ultradian rhythmicity. The lipophilic hormone can rapidly diffuse into cells, although only the pulse peak is of sufficient amplitude to activate the low affinity glucocorticoid receptor (GR). Discrete pulses readily access brain regions such as the hippocampus where GR expression is enriched and known to regulate neuronal function, including memory and learning processes. In the present study, we have tested the hypothesis that GR brain targets are responsive to ultradian GC rhythmicity. We have used adrenalectomised rats replaced with pulses of corticosterone to determine the transcriptional effects of ultradian pulses in the hippocampus. Confocal microscopy confirmed that each GC pulse results in transient GR nuclear localisation in hippocampal CA1 neurones. Concomitant GR activation and DNA binding was demonstrated by synthetic glucocorticoid response element oligonucleotide binding, and verified for the Clock gene Period 1 promoter region by chromatin immunoprecipitation assays. Strikingly each GC pulse induced a 'burst' of transcription of Period 1 measured by heterogeneous nuclear RNA quantitative polymerase chain reaction. The net effect of pulsatile GC exposure on accumulation of the mature transcript was also assessed, revealing a plateau of mRNA levels throughout the time course of pulsatile exposure, indicating the pulse timing works optimally for steady state Per1 expression. The plateau dropped to baseline within 120 min of the final pulse, indicating a relatively short half-life for hippocampal Per1. The significance of this strict temporal control is that any perturbation to the pulse frequency or duration would have rapid quantitative effects on the levels of Per1. This in turn could affect hippocampal function, especially circadian related memory and learning processes. [ABSTRACT FROM AUTHOR]
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- 2010
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12. Recovery from Disrupted Ultradian Glucocorticoid Rhythmicity Reveals a Dissociation Between Hormonal and Behavioural Stress Responsiveness.
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Sarabdjitsingh, R. A., Spiga, F., Oitzl, M. S., Kershaw, Y., Meijer, O. C., Lightman, S. L., and de Kloet, E. R.
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ULTRADIAN rhythms , *GLUCOCORTICOIDS , *HYPOTHALAMIC-pituitary-adrenal axis , *NEUROENDOCRINE cells , *NEUROENDOCRINOLOGY - Abstract
Ultradian release of glucocorticoids is thought to be essential for homeostasis and health. Furthermore, deviation from this pulsatile release pattern is considered to compromise resilience to stress-related disease, even after hormone levels have normalised. In the present study, we investigate how constant exposure to different concentrations of corticosterone affects diurnal and ultradian pulsatility. The rate of recovery in pulsatile hypothalamic-pituitary-adrenal (HPA) activity after withdrawal of exogenous corticosterone is also examined. Finally, the behavioural and neuroendocrine responsiveness to an audiogenic stressor is studied. Adrenally intact male rats were subcutaneously implanted with vehicle, 40% or 100% corticosterone pellets for 7 days. The continuous release of corticosterone from these implants abolished diurnal and ultradian corticosterone variation, as measured with high-frequency automated blood sampling. Pellet removal on post-surgery day 8 allowed rapid recovery of endogenous rhythms in animals previously exposed to daily average concentrations (40%) but not after exposure to high concentrations (100%) of corticosterone. Behavioural and neuroendocrine responsiveness to stress was distinctly different between the treatment groups. Audiogenic stimulation 1 day after pellet removal resulted in a similar corticosterone response in animals previously exposed to 40% corticosterone or vehicle. The 40% pellet group, however, showed less and shorter behavioural activity (i.e. locomotion, risk assessment) to noise stress compared to 100% corticosterone and vehicle-treated animals. In conclusion, unlike the animals impanted with 100% corticosterone, we find that basal HPA axis activity in the 40% group, which had mean daily levels of circulating corticosterone in the physiological range, rapidly reverts to the characteristic pulsatile pattern of corticosterone secretion. Upon reinstatement of the ultradian rhythm, and despite the fact that these animals did not differ from controls in their response to noise stress, they did show substantial changes in their behavioural response to stress. [ABSTRACT FROM AUTHOR]
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- 2010
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13. Gonadotrophin-Releasing Hormone Pulse Generator Activity in the Hypothalamus of the Goat.
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Ohkura, S., Takase, K., Matsuyama, S., Mogi, K., Ichimaru, T., Wakabayashi, Y., Uenoyama, Y., Mori, Y., Steiner, R. A., Tsukamura, H., Maeda, K.-I., and Okamura, H.
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GONADOTROPIN releasing hormone , *HYPOTHALAMUS , *GONADOTROPIN , *ULTRADIAN rhythms , *PULSE generators - Abstract
Pulsatile release of gonadotrophin-releasing hormone (GnRH) is indispensable to maintain normal gonadotrophin secretion. The pulsatile secretion of GnRH is associated with synchronised electrical activity in the mediobasal hypothalamus (i.e. multiple unit activity; MUA), which is considered to reflect the rhythmic oscillations in the activity of the neuronal network that drives pulsatile GnRH secretion. However, the cellular source of this ultradian rhythm in GnRH activity is unknown. Direct input from kisspeptin neurones in the arcuate nucleus (ARC) to GnRH cell bodies in the medial preoptic area or their terminals in the median eminence could be the intrinsic source for driving the GnRH pulse generator. To determine whether kisspeptin signalling could be responsible for producing pulsatile GnRH secretion, we studied goats, measured plasma levels of luteinising hormone (LH) and recorded MUA in the posterior ARC, where the majority of kisspeptin neuronal cell bodies are located. Rhythmic volleys of MUA were found to be accompanied by LH pulses with regular intervals in the ARC, where kisspeptin neuronal cell bodies were found. Exogenous administration of kisspeptin stimulated a sustained increase in LH secretion, without influencing MUA, suggesting that the GnRH pulse generator, as reflected by MUA, originated from outside of the network of GnRH neurones, and could plausibly reflect the pacemaker activity of kisspeptin neurones, whose projections reach the median eminence where GnRH fibres project. These observations suggest that the kisspeptin neurones in the ARC may be the intrinsic source of the GnRH pulse generator. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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14. Ultradian rhythms in Arabidopsis thaliana leaves in microgravity.
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Solheim, B. G. B., Johnsson, A., and Iversen, T.-H.
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ARABIDOPSIS thaliana , *ULTRADIAN rhythms , *REDUCED gravity environments , *FOURIER transform infrared spectroscopy , *PHYSIOLOGICAL effects of gravity , *LEAF physiology , *PHYSIOLOGY - Abstract
• Ultradian movements of Arabidopsis thaliana rosette leaves were discovered and studied under microgravity conditions in space. Weightlessness revealed new facets of these movements. The European Modular Cultivation System (EMCS) was used in a long-term white-light, light-darkness (LD; 16 : 8 h) experiment on the International Space Station (ISS). • Leaves reacted with slow up or down movement (time constant several hours) after transitions to darkness or light, respectively. Superimposed movements with periods of c. 80–90 min and small-amplitude pulsed movements of 45 min were present in the light. Signal analysis (fast Fourier transform (FFT) analysis) revealed several types and frequencies of movements. Identical phase coupling was observed between the 45-min movements of the leaves of one plant. In darkness, movements of c. 120-min period were recorded. • The EMCS allowed 0- g to 1- g transitions to be created. Leaves on plants germinated in microgravity started a negative gravitropic reaction after a delay of c. 30 min. Leaves grown on a 1- g centrifuge reacted to the same transition with an equal delay but had a weaker gravitropic response. • The experiments provide unequivocal demonstrations of ultradian, self-sustained rhythmic movements in A. thaliana rosette leaves in the absence of the effect of gravity. [ABSTRACT FROM AUTHOR]
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- 2009
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15. Relationship between depressive mood and chronotype in healthy subjects.
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Hidalgo, Maria Paz, Caumo, Wolnei, Posser, Michele, Coccaro, Sônia Beatriz, Camozzato, Ana Luiza, and Chaves, Márcia Lorena Fagundes
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CIRCADIAN rhythms , *ULTRADIAN rhythms , *MENTAL depression , *MOOD (Psychology) , *PERINATAL mood & anxiety disorders , *SELF-perception - Abstract
Aim: The endogenous circadian clock generates daily variations of physiological and behavior functions such as the endogenous interindividual component (morningness/eveningness preferences). Also, mood disorders are associated with a breakdown in the organization of ultradian rhythm. Therefore, the purpose of the present study was to assessed the association between chronotype and the level of depressive symptoms in a healthy sample population. Furthermore, the components of the depression scale that best discriminate the chronotypes were determined. Methods: This cross-sectional study involved 200 volunteers, aged 18–99 years, 118 women and 82 men. The instruments were the Montgomery–Äsberg Depression Rating Scale (MADRS), the Morningness/Eveningness Questionnaire, the Self-Reporting Questionnaire-20, and the future self-perception questionnaire. Results: Logistic regression showed that subjects with the eveningness chronotype had a higher chance of reporting more severe depressive symptoms compared to morning- and intermediate-chronotypes, with an odds ratio (OR) of 2.83 and 5.01, respectively. Other independent cofactors associated with a higher level of depressive symptoms were female gender (OR, 3.36), minor psychiatric disorders (OR, 3.70) and low future self-perception (OR, 3.11). Younger age, however, was associated with a lower level of depressive symptoms (OR, 0.97). The questions in the MADRS that presented higher discriminate coefficients among chronotypes were those related to sadness, inner tension, sleep reduction and pessimism. Conclusion: Identification of an association between evening typology and depressive symptoms in healthy samples may be useful in further investigation of circadian typology and the course of depressive disease. [ABSTRACT FROM AUTHOR]
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- 2009
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16. Redox rhythmicity: clocks at the core of temporal coherence.
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Lloyd, David and Murray, Douglas B.
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ULTRADIAN rhythms , *CIRCADIAN rhythms , *YEAST fungi genetics , *PROTISTA , *NAD(P)H dehydrogenases , *MITOCHONDRIAL DNA - Abstract
The article focuses on the ultradian and circadian clock-coupled rhythms in yeasts and protists. A temperature-compensated clock with a period of about an hour provides the time base upon which all central processes are controlled. This system has a redox cycle involving nicotinamide adenine dinucleotide (NADPH) and dithiol-disulfide interconversions, which is closely correlated with the activities of mitochondria.
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- 2007
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17. Involvement of protein kinases in self-organization of the rhythm of protein synthesis by direct cell–cell communication
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Brodsky, Vsevolod Y., Zvezdina, Natalia D., Fateeva, Valentina I., and Malchenko, Ludmila A.
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PROTEIN kinases , *PROTEIN synthesis , *CELL communication , *ULTRADIAN rhythms - Abstract
Abstract: Primary cultures of rat hepatocytes grown on slides were studied in serum-free medium. Ultradian protein synthesis rhythm was used as a marker of synchronization of individual oscillations, resulting in the formation of a common rhythm of the cell population, i.e. cell–cell self-organization. Dense synchronous and sparse non-synchronous cultures were used to estimate effect of protein kinase activity on the kinetics of protein synthesis. Treatment of dense cultures with the inhibitors H7 (40μM) or H8 (25μM) resulted in a loss of the protein synthesis rhythm, a suppression of the cell–cell self-organization. Stimulation of protein kinase activity with either 0.5 or 1.0μM phorbol 12-miristate-13-acetate (PMA) or 10μM forskolin caused the appearance of the synthetic rhythm in non-synchronous sparse cultures under otherwise normal conditions. Inhibition of protein kinase activity with H7 resulted in signal factors, such as gangliosides and phenylephrine, failing to initiate this rhythm in sparse cultures. Activation of protein kinase activity with PMA shifted the phase pattern of the protein synthesis rhythm. Thus, according to our previous and the new data, protein kinase activity and consequently protein phosphorylation is the crucial step of sequence of processes resulting in synchronization during self-organization of cells in producing a common rhythm in the population. The general pathway can be presented as follows: signaling of gangliosides or other calcium agonists→efflux of calcium ion from intracellular stores, with elevation of calcium concentration in the cytoplasm→activation of protein kinases→protein phosphorylation→synchronization of individual oscillations in protein synthesis rates→induction of a common rhythm throughout this population. The data have been discussed concerning similarity of the direct cell–cell communication and the cell self-organization in cultures and in organism. [Copyright &y& Elsevier]
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- 2007
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18. Direct cell-cell communication: a new approach derived from recent data on the nature and self-organisation of ultradian (circahoralian) intracellular rhythms.
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Brodsky, Vsevolod Ya.
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ULTRADIAN rhythms , *CELL communication , *BIOLOGICAL rhythms , *CELLULAR control mechanisms , *PHYSIOLOGICAL control systems - Abstract
Recent data concerning ultradian (circahoralian) intracellular rhythms are used to assess the biochemical mechanisms of direct cell-cell communication. New results and theoretical considerations suggest a fractal nature of ultradian rhythms and their self-organisation. The fundamental and innate nature of these rhythms relates to their self-similarity at different levels of cell and tissue organisation. They can be detected in cell-free systems as well as in cells and organs in vivo. Such rhythms are a means of finding an optimal state of cell function rather than achieving a state of absolute stability. As a consequence, oscillations, being irregular and numerous by the set of periods, are resilient to functional overload and injury. Recent data on the maintenance of their fractal structure and, especially on the selection of optimal periods are discussed. The positive role of chaotic dynamics is stressed. The ultradian rhythm of protein synthesis in hepatocytes in vitro was used as a marker of direct cell-cell communication. The system demonstrates cell cooperation and synchronisation throughout the cell population, and suggests that the ultradian rhythms are self-organised. These observations also led to the detection of mechanisms of direct cell-cell communication in which extracellular factors have an essential role. Experimental evidence indicated the involvement of gangliosides and/or catecholamines in this large-scale synchronisation of protein synthesis. The response of all, or a major part, of the cell population is important; after the initial trigger effect, a periodic pattern is retained for some time. The influence of Ca2+-dependent protein kinases on protein phosphorylation can be a final step in the phase modulation of rhythms during cell-cell synchronisation. The intercellular medium plays an important role in self-synchronisation of ultradian rhythms between individual cells. Low cooperative activity of hepatocytes of old rats resulted from altered composition of the intercellular medium rather than direct effects of animal and cellular ageing. Similarly, in the whole body, changes in levels of gangliosides and catecholamines in the blood serum, a natural intercellular medium, can be critical events in age-dependent changes of the serum and accordingly cell-cell synchronisation. Hepatocytes of old rats exhibit some of the properties of young cells following an increase in blood serum ganglioside level, as well as, in in vitro conditions, after the addition of gangliosides to the culture medium. Together with data on ultradian functional and metabolic rhythms, all the material reviewed here allows us to propose a mechanism of direct cell-cell cooperation via the medium in which the cells exist, that supplements the nervous and hormonal central regulation of organ functions. Ultradian intracellular rhythms may thus provide a finer framework within which the integrated dynamics of respiration, heart rate, brain activity, and even behavioural patterns, are brought to an optimal functional pattern. Innate and direct cell-cell cooperation may have been employed as a means of intercellular regulation during the course of metazoan evolution, that preceded nervous regulation and is presently retained in mammals. [ABSTRACT FROM AUTHOR]
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- 2006
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19. Short-term homeostasis of REM sleep assessed in an intermittent REM sleep deprivation protocol in the rat.
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OCAMPO-GARCÉS, ADRIÁN and VIVALDI, ENNIO A
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HOMEOSTASIS , *RAPID eye movement sleep , *SLEEP-wake cycle - Abstract
An intermittent rapid eye movement (REM) sleep deprivation protocol was applied to determine whether an increase in REM sleep propensity occurs throughout an interval without REM sleep comparable with the spontaneous sleep cycle of the rat. Seven chronically implanted rats under a 12 : 12 light–dark schedule were subjected to an intermittent REM sleep deprivation protocol that started at hour 6 after lights-on and lasted for 3 h. It consisted of six instances of a 10-min REM sleep permission window alternating with a 20-min REM sleep deprivation window. REM sleep increased throughout the protocol, so that total REM sleep in the two REM sleep permission windows of the third hour became comparable with that expected in the corresponding baseline hour. Attempted REM sleep transitions were already increased in the second deprivation window. Attempted transitions to REM sleep were more frequent in the second than in the first half of any 20-min deprivation window. From one deprivation window to the next, transitions to REM sleep changed in correspondence to the amount of REM sleep in the permission window in-between. Our results suggest that: (i) REM sleep pressure increases throughout a time segment similar in duration to a spontaneous interval without REM sleep; (ii) it diminishes during REM sleep occurrence; and (iii) that drop is proportional to the intervening amount of REM sleep. These results are consistent with a homeostatic REM sleep regulatory mechanism that operates in the time scale of spontaneous sleep cycle. [ABSTRACT FROM AUTHOR]
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- 2002
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20. Ultradian clocks in eukaryotic microbes: from behavioural observation to functional genomics.
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Kippert, Fred and Haunt, Paul
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ULTRADIAN rhythms , *EUKARYOTIC cells , *SCHIZOSACCHAROMYCES pombe , *GENETICS - Abstract
Focuses on the homeostasis found in the ultradian clocks of eukaryotic microbes. Control of ultradian clock over respiration and cell cycle in Tetrahymena; Background on the ultradian clock of fission yeast; Molecular genetic analysis of Schizosaccharomyces pombe.
- Published
- 2000
- Full Text
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21. A chaotic systems analysis of the nasal cycle.
- Author
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Winkler, Michael and Combs, Allan
- Subjects
- *
CHAOS theory , *ULTRADIAN rhythms , *NASAL cavity , *PHYSIOLOGY - Abstract
Describes the nasal cycle from a nonlinear chaotic systems perspective. Attractor reconstructions; Fractal dimension; Frequency spectra; Individual differences; Advantages of chaotic systems analysis.
- Published
- 1994
- Full Text
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22. Thirty-Six Hour Correspondence Between Performance and Sleepiness Cycles.
- Author
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Lavie, P., Gopher, D., and Wollman, M.
- Subjects
- *
SLEEP deprivation , *DROWSINESS , *ULTRADIAN rhythms , *CIRCADIAN rhythms , *ATTENTION , *PERFORMANCE , *SLEEP - Abstract
The present work investigates the correspondence between rhythmicity in performance efficiency and sleepiness. Eight subjects kept a repeating schedule of 7 min in bed, 13 min awake out of bed, for two 36-hr periods. Each 36-hr period followed 28 hrs of sleep deprivation. Periods were separated by a one-week interval, Time in bed was subject to two experimental conditions, either attempting or resisting sleep. During each 13-mm period outside the bedroom, subjects were tested on a choice reaction time task with three levels of movement difficulty. In both the attempting sleep and resisting sleep conditions, reaction time and movement time showed marked circadian modulation, generally matching the sleepiness cycle. There was no interaction between movement difficulty and the effects of sleep loss. There were no significant differences in total sleep between the conditions of attempting and resisting sleep; however, subjects instructed to resist sleep had slower reaction times and less stable movement times. The significance of these findings is discussed in terms of differences between attentional mechanisms and multiple processing resources. Results support a theory that the performance and sleep wake cycles are not causally related but rather, may be regulated independently. [ABSTRACT FROM AUTHOR]
- Published
- 1987
- Full Text
- View/download PDF
23. Spontaneous Vigilance Fluctuations in the Daytime.
- Author
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Okawa, Masako, Matousek, Milos, and Petersén, Ingemar
- Subjects
- *
VIGILANCE (Psychology) , *ELECTROENCEPHALOGRAPHY , *STATISTICS , *ULTRADIAN rhythms , *RESEARCH , *PSYCHOPHYSIOLOGY - Abstract
Spontaneous fluctuations of vigilance during the daytime were studied in 412 electroencephalographic (EEG) records from 9 subjects. The EEGs were recorded repeatedly 19-25 rimes between 0800 and 1900 in each subject. Except during the 5-min recording periods when seated subjects were examined with their eyes closed, the subjects were encouraged to engage in their normal daytime activities, such as reading and knitting. The changes in vigilance level were indicated by EEG measures based on automatic analysis. Statistical analyses of the data showed that vigilance fluctuations occurred rhythmically with a period between 60 and 110 min. The ultradian vigilance rhythms were detectable even though the subjects were engaged in normal daytime activity. Individual patterns of ultradian rhythms were, however, observed to be relatively unstable when within-subjects comparisons were made between experiments conducted one to six weeks apart. [ABSTRACT FROM AUTHOR]
- Published
- 1984
- Full Text
- View/download PDF
24. Biological Rhythms in Arousal Indices: A Potential Confounding Effect in EEG Biofeedback.
- Author
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Gertz, John and Lavie, Peretz
- Subjects
- *
ULTRADIAN rhythms , *ELECTROENCEPHALOGRAPHY , *BIOFEEDBACK training , *CIRCADIAN rhythms , *PARADIGM (Theory of knowledge) - Abstract
Several investigators have observed ultradian rhythmicities in physiological indices of arousal. Although EEG biofeedback has been widely explored as a means of auto-regulating cortical arousal, alpha or theta enhancement has not yet been convincingly demonstrated in comparison to continuous baseline controls for the possible effect of endogenous cyclical arousal trends. Diurnal EEG and subjectively appraised arousal measures were recorded from 11 subjects on a 5-min recording, 5- min recovery schedule, continuously over 7½ hrs. Subjects returned to the laboratory for an equal amount of recording during which they attempted to either raise or lower the frequency of their EEG with the aid of biofeedback. Significant ultradian rhythmicity centered at about 200 min/cycle was observed in EEG measures and in subjectively appraised arousal. Although eyes-open frequency- raising and frequency-lowering biofeedback training was efficacious in comparison to long-day baselines, eyes-closed frequency-lowering training was not, lending support to other studies which have failed to achieve overall eyes-closed alpha or theta enhancement even with many hours of training. Because the observed ultradian and circadian EEG rhythmicities could be spuriously interpreted as learning curves under a biofeedback paradigm, it is argued that future designs should incorporate continuous baseline controls. [ABSTRACT FROM AUTHOR]
- Published
- 1983
- Full Text
- View/download PDF
25. The REM Cycle in Altered Sleep/Wake Schedules.
- Author
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Moses, J., Naiton, P., and Johnson, L. C.
- Subjects
- *
RAPID eye movement sleep , *SLEEP-wake cycle , *SLEEP , *ULTRADIAN rhythms - Abstract
The length and rhythmicity of the REM cycle was studied using data from three laboratories. In the three studies, 25 subjects obtained their sleep in naps under three different sleep/wake schedules: 60/160 main (N=8), 30/60 min (N=10), and 60/120 mill (N-7), over a period of 40 his to l0 days. Previous results from these subjects (Moses, Lubin, Johnson, & Naltoh, 1977) indicated that the REM cycle is sleep-dependent, rather than an expression of an ongoing Basic RestActivity Cycle (BRAC). As a further test of the sleep-dependent hypothesis, autocorrelation and r[SUP2] analysis was applied to the compressed sleep (i.e., all wake time between and within sleep periods subtracted) of the baseline, nap, and recovery conditions. Compared to baseline, there were no significant differences in nap REM cycle length in the 60/160 and 60/120 groups; the 30/60 group had significantly shorter cycles. It appeared that this REM cycle shortening was due to the significantly shorter REM episodes in this group. The nap r[SUP2]values were significantly lower than baseline in the 30/60 and 60/120 groups, indicating increased variability in the timing of REM episodes during naps. AH the nap r[SUP2] values, however, were significantly larger than those obtained from a random distribution of sleep stages. To further examine the effects of the degree of sleep fragmentation on REM cycle rhythmicity, two additional groups of subjects whose sleep was fragmented by either REM or SWS deprivation were compared to the nap groups. REM deprivation was the most disruptive of REM cycle rhythmicity; the r[SUP2] values for REM deprivation were significantly less than those for napping or SWS deprivation. These data offer further support that the REM cycle is a sleep-dependent rhythm and is not an expression of an ongoing BRAC. [ABSTRACT FROM AUTHOR]
- Published
- 1978
- Full Text
- View/download PDF
26. Temporal Distribution and Ontogenetic Development of EEG Activity During Sleep.
- Author
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Keane, Barry, Smith, Jack, and Webb, Wilse
- Subjects
- *
BIOLOGICAL rhythms , *ULTRADIAN rhythms , *RAPID eye movement sleep , *ONTOGENY , *ELECTROENCEPHALOGRAPHY , *AGE groups - Abstract
The purpose of this study was to investigate nightly patterns of temporal organization of EEG alpha, beta, delta, and sigma spindle activities and to measure changes in these patterns with age. A total of 50 nights of EEG recordings were obtained from normal subjects from various age groups, ranging from 3 to 79 yrs. A Sleep Analyzing Hybrid Computer (SAHC) measured min by rain amounts of each EEG waveform. The amount of beta activity occurring in the first half of the night increased with age, whereas the amount occurring later in the night decreased. An opposing trend was observed in the occurrence of delta activity. Alpha activity increased significantly for subjects in their 50's and increased tremendously after age 65. In the oldest group the alpha had developed a very definite ultradian pattern and appeared coincident with REM. This alpha-REM pattern was suppressed in the younger age groups. [ABSTRACT FROM AUTHOR]
- Published
- 1977
- Full Text
- View/download PDF
27. Short period leaf movements in Oxalis regnellii.
- Author
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Pedersen, Marit, Johnsson, Anders, M&Ehle, Jørgen, and Dalløkken, Runar
- Subjects
- *
OXALIS , *ULTRADIAN rhythms , *LEAVES , *PETIOLES , *BIOLOGICAL rhythms , *PLANT stems - Abstract
Oxalis regnellii Mig. is a trifoliate plant, and the three leaflets usually show synchronized up and down movements with a circadian period of 26–27 h. The three leaflets can also perform desynchronized ultradian oscillations, and we report on such rhythms under different conditions. A study of the occurrence of ultradian leaf movement rhythms as a function of irradiance is presented. At an irradiance of approximately 1 μW cm−2, the occurrence was maximal and ca 30%. The periods varied from 5 to 15 h. Four other cases of ultradian rhythms in different conditions are also presented. In one case spontaneous ultradian rhythms occurred, and in another, two of the leaflets showed ultradian rhythms when the third leaflet had received a light pulse. In two more cases, the three leaflets on a leaf were separated by physical cuts along the petiole between the pulvini; in both cases the period was approximately 5 h. Possible mechanisms to explain the ultradian rhythms in Oxalis regnelli are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 1993
- Full Text
- View/download PDF
28. A method to record circadian plant movements, with application to Oxalis leaf rhythms.
- Author
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Pedersen, Marit, Eidesmo, Terje, and Jobnsson, Anders
- Subjects
- *
CIRCADIAN rhythms , *OXALIS , *TRANSDUCERS , *ULTRADIAN rhythms , *LEAVES , *BIOLOGICAL rhythms - Abstract
A transducer was developed to record the circadian movement of the individual leaflets in Oxalis regnelli Mig. The method can easily be adapted to measure other kinds of plant movements as well. It is based on the detection of the shadow each leaflet casts on the small side of a specially formed Perspex plate. The light is guided through the Perspex and collected by a phototransistor, which provides an electrical signal that is proportional to the light intensity falling onto it. The output signal can be made a linear function of the leaf angle. This equipment was used in experiments to study the coupling between the 3 leaflets in Oxalis. Pulses of 4 h of red light were given to one of the leaflets,the two others were shielded from the light. A phase response curve was determined for each leaflet, but there was no significant difference in the phase response between the 3 leaflets. Experiments were also made in which the 3 leaflets were separated physically by cuts along the petiole between the pulvini. In this case ultradian oscillations were observed. [ABSTRACT FROM AUTHOR]
- Published
- 1992
- Full Text
- View/download PDF
29. Characteristics of the Circadian Activity Rhythm in Common Marmosets (Callithrix j. jacchus).
- Author
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Erkert, Hans G.
- Subjects
- *
MARMOSETS , *CIRCADIAN rhythms , *ULTRADIAN rhythms , *CALLITHRIX jacchus , *CALLITHRIX , *PRIMATES - Abstract
The circadian activity rhythm of the common marmoset, Callithrix j. jacchus was investigated by long-term recording of the locomotor activity of 15 individuals (5 males, 10 females) from 1.5 to 8 years old, both under constant illumination and under LD 12:12. The mean period of the spontaneous circadian rhythm was 23.2 ± 0.3 h. Neither sex-specific differences nor a systematic influence of light intensity on the spontaneous period were observed, but the period was dependent on the duration of the trial and on the age of the individual. Due to the short spontaneous period, in LD 12:12 there was a distinct advance of the activity phase with respect to the light time and a masking of the true onset of activity by the inhibitory direct effect of low light intensity during the dark time. After an 8 h delay shift of the LD 12:12, re-entrainment of the circadian activity rhythm required an average of 6.8 ± 0.7 days; the average re-entrainment time after an 8 h phase advance of the LD cycle was 8.6 ± 1.3 day. This directional effect is ascribed to characteristics of the phase-response curve. No ultradian components were observed, either in the LD-entrained or the free-running circadian activity rhythm. [ABSTRACT FROM AUTHOR]
- Published
- 1989
- Full Text
- View/download PDF
30. Ultradian Periodicities in EEG and Behavior in the Squirrel Monkey (Saimiri sciureus).
- Author
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Ehlers, C. L. and Foote, S. L.
- Subjects
- *
ULTRADIAN rhythms , *BIOLOGICAL rhythms , *ANIMAL mechanics , *ELECTROENCEPHALOGRAPHY , *ANIMAL behavior , *SQUIRREL monkeys , *ZOOLOGY , *PRIMATES - Abstract
This report describes periodic oscillations in electroencephalographic (EEG) and behavioral activity with a cycle length of 15–30 seconds in chair-restrained squirrel monkeys (Saimiri sciureus). These oscillations consisted of alternating episodes of vigilance, characterized by visual scanning and motor movement, and inattentiveness, characterized by behavioral quiescence with little eye or limb movement. During vigilance the EEG exhibited low-amplitude, high-frequency (> 16 Hz) activity. During quiescent periods, a high-amplitude synchronized EEG was present with activity in the 8–16-Hz band predominating. The presence or frequency of this EEG and behavioral periodicity was not modified by time of day, as no difference was found between morning and afternoon recording sessions. Although the factors or mechanisms responsible for this rhythm are unclear, it should be noted by those investigators studying the behavior or neurophysiology of Saimiri sciureus in the laboratory setting. [ABSTRACT FROM AUTHOR]
- Published
- 1984
- Full Text
- View/download PDF
31. Ontogeny of Ultradian and Nocturnal Activity Rhythms in the Isolated Albino Rat.
- Author
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Teicher, Martin H. and Flaum, Lawrence E.
- Subjects
RATS ,BIOLOGICAL rhythms ,MURIDAE ,DEVELOPMENTAL biology ,AGE groups ,ULTRADIAN rhythms - Abstract
The activity of isolated rats from 6 to 25 days of age was analyzed at 10-mm intervals. Ultradian peak activity rhythms, with a rough 1-2-hr periodicity, developed between 9 and 12 days of age, and reached an extreme at 15 days. Ultradian periods of attenuated activity were however detectable even in 6-day-olds. Isolated rats at 15 days of age displayed greatly accentuated profiles characterized not only by heightened activity levels; but by an extreme cyclicity. These subjects spent most of their time oscillating between periods of marked activity and marked inactivity. Both the average and total duration of these extreme periods were greater in 15-day-olds than any of the other ages. Free-running nocturnal activity rhythms were also observed to develop in isolated rats tested in continuous darkness by the 15th day. [ABSTRACT FROM AUTHOR]
- Published
- 1979
- Full Text
- View/download PDF
32. Microcomputer-gestütztes Telemetriesystem zur Erfassung ultradianer Temperaturrhythmik beim Großtier.
- Author
-
Mohr, E. and Leuschner, Th.
- Abstract
A Microcomputer Assisted Telemetric System for Recording of Ultradian Core Temperature Fluctuations in Farm Animals A radiotelemetry system for measurement of deep body temperature in unrestrained farm animals is presented. Because the main attention is set on the small ultradian temperature rhythms, a system with high sensitivity (0.05°C) and little transmission-interferences (high field intensity of the transmitter) was developed. Circuit diagrams of the implantable thermoprobe and the basic principles of the recording unit are pointed out. Management of measurement as well as recording of data is software-controlled by a microcomputer. Further computerized processing presupposes that there is no incorrect data. Therefore the complete elimination of interferences is carried out automatically by a computer. The algorithm used for this is described in detail. Zusammenfassung Es wird ein Radiotelemetriesystem zur Messung der Körperkerntemperatur beim freibeweglichen Großtier vorgestellt. Um auch ultradiane Temperaturschwankungen sicher messen zu können, wurde besonderer Wert auf hohe Auflösung (0,05°C) und störungsarme übermittlung (hohe Feldstärke des Senders) gelegt. Es werden die Baupläne der implantierbaren Sonde sowie die Funktionsprinzipien der Empfangsanlage dargestellt. Steuerung der Meßwerterfassung sowie die Speicherung der Daten erfolgt software-gesteuert durch einen Microcomputer. Die Störungsbeseitigung - als Voraussetzung zur Weiterverarbeitung der Rohdaten - erfolgt automatisch im angeschlossenen Computer. Der hierfür notwendige Rechenalgorithmus wird ausführlich beschrieben. [ABSTRACT FROM AUTHOR]
- Published
- 1989
- Full Text
- View/download PDF
33. EEG Delta Activity During Human Sleep as a Damped Ultradian Rhythm.
- Author
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Lubin, Ardie, Nute, Cyril, Naitoh, Paul, and Martin, Willaim B.
- Subjects
- *
ELECTROENCEPHALOGRAPHY , *SLEEP , *ULTRADIAN rhythms , *SINE waves - Abstract
EEG delta activity during human sleep has a rhythmic pattern resembling a damped sinusoid with a period of about 100 min. Although the REM episodes coincide with the troughs of the delta cycle, the two rhythms are semi-independent. [ABSTRACT FROM AUTHOR]
- Published
- 1973
- Full Text
- View/download PDF
34. CSF hypocretin-1 (orexin-A) concentrations in narcolepsy with and without cataplexy and idiopathic hypersomnia.
- Author
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KANBAYASHI, TAKASHI, INOUE, YUICHI, CHIBA, SHIGERU, AIZAWA, RIKA, SAITO, YASUSHI, TSUKAMOTO, HARUKO, FUJII, YUKIHARU, NISHINO, SEIJI, and SHIMIZU, TETSUO
- Subjects
- *
CEREBROSPINAL fluid , *NARCOLEPSY - Abstract
We measured cerebrospinal fluid (CSF) hypocretin-1 levels in 11 patients with narcolepsy–cataplexy, five with narcolepsy without cataplexy and 12 with idiopathic hypersomnia (IHS). All patients were Japanese. As reported in Caucasian patients, undetectable or very low hypocretin-1 levels were observed in most (9 out of 11) Japanese narcolepsy–cataplexy patients. Our hypocretin-deficient narcoleptics included three prepubertal cases within few months after the disease onset. All nine hypocretin-deficient patients were human leuckocyte antigen (HLA) DR2 positive, while two who had normal CSF hypocretin-1 levels were HLA DR2 negative. In contrast, none of the narcolepsy without cataplexy and IHS subjects had undetectable low levels. Low CSF hypocretin-1 is therefore very specific for HLA DR2 positive narcolepsy–cataplexy, and the deficiency is likely to be established at the early stage of the disease. [ABSTRACT FROM AUTHOR]
- Published
- 2002
- Full Text
- View/download PDF
35. EFFECTS OF A SINGLE PULSE OF BRIGHT LIGHT ON THE ULTRADIAN RHYTHM OF DIURNAL EEG ACTIVITY.
- Subjects
- *
CIRCADIAN rhythms , *ULTRADIAN rhythms , *BIOLOGICAL rhythms , *ELECTROENCEPHALOGRAPHY - Abstract
An abstract of the article "Effects of a Single Pulse of Bright Light on the Ultradian Rhythm of Diurnal EEG Activity" is presented. A study has been conducted which examines the effects of a bright light towards circadian rhythm in body temperature and sleep-wake ultradian rhythm. Eight student volunteers have participated in the study who were observed with the effects of the high and middle illuminance of the bright light. Information regarding the results of the study is discussed.
- Published
- 2000
36. LACK OF SLEEP/WAKE CIRCADIAN RHYTHMS IN NARCOLEPTIC PATIENTS SUBMITTED TO A 4 HOUR ULTRADIAN REGIMEN.
- Subjects
- *
SLEEP-wake cycle , *CIRCADIAN rhythms , *NARCOLEPSY , *SLEEP disorders , *ULTRADIAN rhythms - Abstract
The article presents an abstract of the study entitled "Lack of Sleep/Wake Circadian Rhythms in Narcoleptic Patients Submitted to a 4 Hour Ultradian Regimen." They have concluded that narcoleptic patients did not exhibit anymore a circadian rhythm of sleep wake patterns after submitting to a 4 Hour Ultradian Regimen The data suggest that an alteration of the circadian sleep wake process might be responsible for the occurrence of an ultradian sleep wake pattern specific of the narcoleptic disease.
- Published
- 2000
37. Sex Differences in Sleep Regulation in Depression.
- Subjects
- *
GENDER differences (Psychology) , *SLEEP , *RAPID eye movement sleep , *DEPRESSED persons , *ULTRADIAN rhythms - Abstract
The article presents the abstract of the study "Sex Differences in Sleep Regulation in Depression." It evaluates the temporal organization of quantitative electroencephalography activity in rapid eye movement sleep, non-rapid eye movement sleep and ultradian rhythm regulation in patients with major depressive disorder.
- Published
- 2000
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