• Biomolecules & Therapeutics
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• v.29 no.1
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• pp.31-40
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• 2021

All living beings on earth have an important mechanism of 24-h periodicity, which controls their physiology, metabolism, and behavior. In humans, 24-h periodicity is regulated by the superchiasmatic nucleus (SCN) through external and environmental cues. Peripheral organs demonstrate circadian rhythms and circadian clock functions, and these are also observed in cultured cell lines. Every cell contains a CLOCK: BMAL1 loop for the generation of circadian rhythms. In this review, we focused on cell autonomous circadian rhythms in immune cells, the inflammatory diseases caused by disruption of circadian rhythms in hormones, and the role of clock genes in inflammatory diseases.

• Sleep Medicine and Psychophysiology
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• v.1 no.1
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• pp.68-75
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• 1994

In order to examine the effects of circadian rhythm in subjective alertness on the occurrence of traffic accidents, the authors investigated the occurrence rate of traffic accidents adjusted to traffic volume in Seoul and the relative rate of fatal accidents versus total traffic accidents in Korea at different times of day in 1991. We analyzed these data in relation with the circadian rhythm in subjective alertness. The results were as follows. Both the occurrence rate of traffic accidents adjusted to traffic volume and the relative rate of fatal accidents versus total traffic accidents were the highest at 3-4 a.m., known as the time period of the lowest subjective alertness. They were negatively correlated with subjective alertness (p<0.05, p<0.001). In conclusion, it is suggested that the circadian rhythm of subjective alertness should have a significant effect on the occurrence of traffic accidents despite many confounding factors such as driving environments.

• Korean Journal of Biological Psychiatry
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• v.24 no.1
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• pp.26-31
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• 2017

Objectives A normal circadian rhythm of autonomic nervous system function stands for the daily change of sympathetic and parasympathetic modulation, which can be measured by heart rate variability (HRV). Generally, patients in the intensive care unit (ICU) are prone to sleep-wake cycle dysregulation, therefore, it may have an influence on the circadian rhythm of autonomic nervous system. This study was designed to interpret possible dysregulation of autonomic nervous system in ICU patients by using HRV. Methods HRV was assessed every 3 hours in 21 ICU patients during a 7-minute period. The statistical differences of HRV features between the morning (AM 6 : 00-PM 12 : 00), and the afternoon (PM 12 : 00-PM 18 : 00) periods were evaluated in time domain and frequency domain. Results Patients showed significantly increased normalized power of low frequencey (nLF), absolute power of low frequencey (LF)/absolute power of high frequencey (HF) in the afternoon period as compared to the morning period. However, normalized power of high frequency (nHF) was significantly decreased in the afternoon period. There was no statistically significant difference between the morning period and the afternoon period in the time domain analysis. Conclusions The increased sympathetic tone in the afternoon period supports possible dysregulation in the circadian rhythm of autonomic nervous system in ICU patients. Future studies can help to interpret the association between autonomic dysregulation and negative outcomes of ICU patients.

• Child Health Nursing Research
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• v.18 no.2
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• pp.85-94
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• 2012

Purpose: Instead of a chaotic non circadian environmental approach, continuing regular day-night rhythm in neonatal nurseries may benefit the development of preterm infants. The purpose of this study was to define the effects of cycled lighting on circadian rhythms of premature infants. Methods: The experimental group included 15 preterm infants, and the control group, 15 premature infants in the NICU of a general hospital in Seoul. All infants were between 32 and 37 weeks' postconceptional age. The experimental group infants were provided with cycled lighting before discharge. The incubator or bassinet cover of the experimental group was off between 7 AM and 7 PM, and was covered between 7 PM and 7 AM. Results: There were significant differences in the NNNS score ($p$=.039), and some significant differences in the sleep-activity pattern between the experimental group and the control group, but distinct differences in sleep-activity patterns between the two groups could not be defined. Conclusion: The results of this study suggest that cycled lighting can be helpful in the neurobehavioral development of preterm infants. By modifying the NICU environment to provide a more developmentally supportive milieu, nursing professionals can better meet the infants' physiologic and neurobehavioral needs.

• Journal of Korean Neurosurgical Society
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• v.65 no.1
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• pp.151-160
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• 2022

Continuous monitoring of intracranial pressure is a well established medical procedure. Still, little is known about long-term behavior of intracranial pressure in normal pressure hydrocephalus. The present study is designed to evaluate periodicity of intracranial pressure over long-time scales using intraventricular pressure monitoring in patients with normal pressure hydrocephalus. In addition, the circadian and diurnal patterns of blood pressure and body temperature in those patients are studied. Four patients, selected with "probable" normal pressure hydrocephalus, were monitored for several dozen hours. Intracranial pressure, blood pressure, and body temperature were recorded hourly. Autocorrelation functions were calculated and cross-correlation analysis were carried out to study all the time-series data. Autocorrelation results show that intracranial pressure, blood pressure, and body temperature values follow bimodal (positive and negative) curves over a day. The cross-correlation functions demonstrate causal relationships between intracranial pressure, blood pressure, and body temperature. The results show that long-term fluctuations in intracranial pressure exhibit cyclical patterns with periods of about 24 hours. Continuous intracranial pressure recording in "probable" normal pressure hydrocephalus patients reveals circadian fluctuations not related to the day and night cycle. These fluctuations are causally related to changes in blood pressure and body temperature. The present study reveals the complete loss of the diurnal blood pressure and body temperature rhythmicities in patients with "probable" normal pressure hydrocephalus.

• Proceedings of the KSAR Conference
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• 2004.06a
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• pp.261-261
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• 2004

Circadian rhythms, which measure time about 24 hours, are generated by one of the most ubiquitous and well investigated timing system. More recently, circadian clock gene expression has been reported in various peripheral tissues. If a circadian clock is functioning in the testis, expression of clock genes should be observed in this tissue. To resolve this issue, we examined the expression of circadian clock genes in the testis. (omitted)

• Proceedings of the Korea Society of Design Studies Conference
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• 2004.05a
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• pp.126-127
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• 2004

• Journal of Life Science
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• v.28 no.8
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• pp.985-991
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• 2018

Biological clocks are the basis of temporal control of metabolism and behavior. These clocks are characterized by autonomous free-running oscillation and temperature compensation and are found in animals, plants, and microorganisms. To date, various biological clocks have been reported. These include clocks governing hibernation, sleep/wake, heartbeat, and courtship song. These clocks can be differentiated by the period of rhythms, for example, infradian rhythms (> 24-hr period), circadian rhythms (24-hr period), and ultradian rhythms (< 24-hr period). In yeast (Saccharomyces cerevisiae), at least five different autonomous oscillations have been reported; (1) glycolytic oscillations (T = 1~30 min), (2) cell cycle-dependent oscillations (T = 2~16 hr), (3) ultradian metabolic oscillations (T = 15~50 min), (4) yeast colony oscillations (T = a few hours), and (5) circadian oscillations (T = 24 hr). In this review, we discuss studies on oscillators, pacemakers, and synchronizers, in addition to the application of biological clocks, to demonstrate the nature of autonomous oscillations, especially ultradian metabolic oscillations of S. cerevisiae.

• Korean Journal of Clinical Pharmacy
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• v.6 no.2
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• pp.1-6
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• 1996

Carcadian rhythm dependence of vancomycin pharmacokinetics was evaluated in 5 normal volunteers receiving a single intravenous 1.0 g dose of vancomycin at 8 o'clock in the morning and another occasion at 8 o'clock in the evening in a crossover manner. The serum data were subjected to simultaneous computer nonlinear least squares regression analysis using a two-compartment pbarmacokinetic model. The mean half-life of vancomycin was $4.78\pm0.81$ hr in the morning and $4.25\pm0.51$ hr in the evening. The mean total body clearance of vancomycin was $1.29\pm0.58$ hr in the morning and $5.58\pm0.48$ hr in the evening. No circadian rhythm was found to be apparent in normal volunteers. The mean in intrasubject difference in the half-life between 8 A.M. and 8 P.M. was $15.4\%$ with fluctuations ranging from $10.4\sim33.8\%$, It is reasonable to consider individual circadian rhythm for effective dosage regimen of vancomycin in clinical chronotherapeutics.

• Proceedings of the Korean Society of Potoscience Conference
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• 2006.06a
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• pp.65-65
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• 2006