• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.2
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• pp.222-228
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• 1984

Since organisms have their rhythms by synchronizing the changes of periodic external circumstances and maintaining the integration of internal ones, circadian rhythm which affects to ingestion, digestion and metabolism of nutrients in the body, is important and interesting to discuss in the field of nutritional science. Also it is a serious public health problem tat various night-shift jobs are increasing now a days. Therefore authors wish to understand the properties of circadian rhythm and the rhythms of metabolic activities.

• Journal of Veterinary Clinics
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• v.15 no.1
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• pp.1-7
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• 1998

The present study was performed to evaluate circadian rhythm of blood nortisol concentration and change of blood cortisol concentration by various stress type in domestic cats. The ELISA kit for cortisol measurement was evaluated on the effective assay range, day to day variation, within-run variation and accuracy. The results were 1-1,000 ng/ ml, 0.7-5.9%, 0.9-4.5% and 98%, respectively. The circadian rhythm of serum cortisol concentration is presented in cats. Change of serum cortisol concentration was also examined with several stressors, stimulation with hamster as a prey, beep electronic sounds, vehicle transportation and unfamiliar environment. Unfamiliar environment showed most remarkable change in serum cortisol level.

• Korean Journal of Biological Psychiatry
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• v.2 no.2
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• pp.266-274
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• 1995

We invesigated whether the circadian rhythms of plasma MHPG and HVA concentrations exist in 11 healthy young adults, and analyzed the patterns of their circadian rhythms. The results were as follows : 1) The change in the mean plasma MHPG concentrations analyzed by repeated measures ANOVA was not statistically significant. Five subjects showed significant circadian rhythms of plasma MHPG concentrations of each individual, and 4 of those had the acrophases between 17PM and 24PM. 2) The change in the mean plasma HVA concentrations analyzed by repeated measures ANOVA was not statistically significant. Six subjects showed significant circadian rhythms of plasma HVA concentrations of each individual, and 4 of those had the acrophases between 21PM and 6AM. In conclusion, the circadian rhythm pattern of plasma HVA concentrations in our result is consistent with the previous study. It was suggested that plasma MHPG and HVA concentrations should be measured more frequently, and the physical activities of subjects be controlled more strictly for the following study.

• The Korean Journal of Zoology
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• v.32 no.4
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• pp.441-449
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• 1989

Azadirachtin은 Leucophaeq muderae (Fabricius연 하루 활동주기길이를 0.16 $\pm$ 0.03 h 단축시켰으며, 실험동물의 40 %에서 리듬의 Splitting현상이 관찰되었다. 하루에 두개의 활동주기를 보이는 Splitting현상은 서로 180$^{\circ}$를 유지하여 나타났고, 이는 동물의 실험 전의 본래 주기길이가 평균보다 더 긴 주기를 지닌 동물에게 주로 나타났다. 또한 활동주기의 Splitting현상을 보이는 동물의 안구와 뇌신경(optic lobe) 절단수술 후 Splitting이 사라짐으로써 Azadirachtin이 뇌신경에 자극을 주어 Splitting을 야기시켰으며, 한쌍의 optic lobe 중 어느 한쪽만으로도 동물의 활동주기 조절가능성이 있다는 것이 본 실험을 통하여 밝혀졌다. Azadirachtin shortens the period length of the locomotor activity rhythm in the circadian rhythm of Leucophoeo maderae and induces splitting of this rhythm in ho components in about 40% of the animals. The phase relationship between the ho components is 180$^{\circ}$Both shortening of period and splitting are more pronounced in animals processing longer periods before the injection of azadirachtin. Splitting disappears after the surgical transection of optic lobe.

• Journal of the Ergonomics Society of Korea
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• v.19 no.3
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• pp.1-12
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• 2000

The Korean version of the morningness-eveningness questionnaire (MEQ) and sleep habits inventory were administered to 1,038 Korean male daytime workers and were analyzed according to age and chronotype to determine what these factors reveal about sleep habits in view of phase difference of circadian rhythm. The mean and distribution of scores on the MEQ moved significantly toward the morning type with aging. Bedtimes and waking times were progressively later from the morning, intermediate, to evening types, and were also earlier with aging. Preferred bedtimes and waking times showed more distinct differences than did the habitual times in each chronotype. The percentage of subjects who answered that sleep length was 'short', mood upon waking was 'bad', and variabilities of bedtime and sleep length were 'large' were greater in the young and evening types than in the elder and morning types, respectively. These findings suggested that subjects were shifted toward the morning type and the phase of circadian rhythm had moved forward with aging. Preferred bedtime and waking time were a better reflection of individual circadian rhythms than habitual bedtime and waking time.

• BMB Reports
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• v.48 no.12
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• pp.677-684
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• 2015

Cardiovascular function is regulated by the rhythmicity of circadian, infradian and ultradian clocks. Specific time scales of different cell types drive their functions: circadian gene regulation at hours scale, activation-inactivation cycles of ion channels at millisecond scales, the heart's beating rate at hundreds of millisecond scales, and low frequency autonomic signaling at cycles of tens of seconds. Heart rate and rhythm are modulated by a hierarchical clock system: autonomic signaling from the brain releases neurotransmitters from the vagus and sympathetic nerves to the heart's pacemaker cells and activate receptors on the cell. These receptors activating ultradian clock functions embedded within pacemaker cells include sarcoplasmic reticulum rhythmic spontaneous Ca²⁺ cycling, rhythmic ion channel current activation and inactivation, and rhythmic oscillatory mitochondria ATP production. Here we summarize the evidence that intrinsic pacemaker cell mechanisms are the end effector of the hierarchical brain-heart circadian clock system.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.1 no.1
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• pp.77-97
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• 1994

The circadian system represents a temporal order which is mediated by the mutual coupling of oscillators and by the synchronizing effects of zeitgebers. It is known that well-being of man depends partly on the maintenance of this order, and that repeated or long lasting disturbances to it such as shift work will Cause harmful effects. This study was a quasi-experimental study to test the effect of shift directions for the clinical nurses on the circadian rhythm. Fourteen nurses working at the general units of Y hospital were selected according to the established criteria. Fourteen subjects were assigned to a weekly shift but the directions of shift work were phase delay first and then phase advance or vice versa. Oral temperature, total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom were measured during these days except holidays. The data collection period was from April 26, 1993 to July 3, 1993. MANOVA and Wilcoxon signed rank test were used for statistical analysis. The results are summarized as follows. 1. Having worked on evening and night shifts in either phase delay or phase advance schedules, temperature rhythms of shift workers were gradually adapted to the new sleep-wake cycles. A complete adaptation to work on the night shift was achieved the sixth day of the night shift in the phase delay schedule compared to the partial adaptation to the work on the night shift in the phase advance schedule. Accordingly, by putting evening shift between day and night shifts, it will be possible for circadian rhythm to adapt easily to the night shift. 2. There were differences in the total sleeping time, frequency of steep-wake cycle, fatigue, and physical symptom except for mental performance between night shift and day, evening shift. This indicates further that shift workers working on the night shift have a hard time adapting to the shift work compared to the other shifts. 3. Evaluating all the acrophases of temperature rhythm either in phase delay or phase ad-vance schedules, it was shown that night to evening shift in the phase ad-vance schedule revealed the smallest phase move. Also phase advance schedule showed poorer adaptation to shift work than phase delay schedule in connection with total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom. It is suggested, taken together, these findings reflect that phase delay schedule facilitated the degree of adjustment to the shift work compared to the phase advance schedule.

• Journal of Photoscience
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• v.9 no.2
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• pp.9-12
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• 2002

Circadian rhythms can be seen in a variety of physiological functions in insects. Light is a powerful zeitgeber not only synchronizing but also modulating the rhythm to adjust insect's temporal structure to seasonal changes in the environmental cycle. There are two general effects of the length of light phase within 24 hr light cycles on the circadian rhythms, i.e., the modulation of free-running period and the waveform. Since the photoperiodic modulation of the free-running period is induced even in the clock mutant flies, per$\^$s/, the free-running period is not fully determined genetically. In crickets, the ratio of activity (a) and rest phase (p) under the constant darkness (DD) is clearly dependent on the photoperiod under which they have been kept. When experienced the longer photoperiod it becomes smaller. The magnitude of change in a/p-ratio is dependent on the number of cycles they experienced. The neuronal activity of the optic lobe in DD shows the a/p-ratio changing with the preceding photoperiod. These data suggest that a single circadian pacemaker stores and maintains the photoperiodic information and that there is a system that accumulates the effects of single photoperiod to cause greater effects.

• Journal of Korean Biological Nursing Science
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• v.3 no.1
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• pp.1-10
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• 2001

뇌손상이라고 하는 과도한 stress를 받았을 때 free cortisol의 분비되는 양과 urinary free cortisol의 circadian 리듬에 어떻게 영향을 주는지 확인하기 위하여 시도하였다. 연구대상은 대조군은 건강한 젊은 여성 6명과 실험군응 CT상 뇌에 손상을 받은 4명의 여성으로 30대 환자이었다. 담당의사와 중환자실 관리책임자의 동의하에서 시도되었으며, 실험기간은 2000년 7월 1일에서 7월 10일까지였다. 대조군과 실험군의 뇨를 채취하여 뇨중 free cortisol 농도의 circadian rhythm을 알아보기 위해 채뇨 후 분석하였다. 채뇨는 뇌손상을 받고 응급실을 통해 신경외과 중환자실에 입원한 지 5시간 이내에 해당된 환자로 24시간 유지되는 foley catherization 상태하에서 12:00부터 3일동안 72시간을 2시간 간격으로 채뇨하였고, 대조군은 오전 12시부터 24시간 동안 2시간 간격으로 채뇨하였다. 측정방법으로는 cortisol의 정량은 solid-phase radioimmuoassay 방법을 이용하였으며, 분석재료는 Coat-A-Count(R) Cortisol kit(DPC, U.S.A.)을 사용하여 DPC사의 측정방법을 따랐다. 연구대상자의 free cortisol의 총량은 대조군에서는 $42.8{\mu}g$이었고, 실험군은 1일에 $991.2{\mu}g$, 2일에 $809{\mu}g$, 3일에 $544.2{\mu}g$으로 대조군과 통계적으로 유의한 차이를 나타내(p<.05), 실험군에서 현저하게 증가된 양상을 보였고, 시간이 지나면서 점점 감소하는 경향을 나타냈다. 시간별로 t-검정으로 분석한 결과로는 모든 시간대에서 대조군과 실험군의 평균치는 통계적으로 유의한 차이를 나타냈다. Free cortisol의 circadian에서는 대조군에서는 정상인의 cortisol의 circadian의 경우와 같은 리듬을 보였으나, 손상을 받은 실험군의 경우 분비량은 현저하게 증가했음을 보여주었다. 최고치가 제1일에 18:00과 다음날 10:00에 나타나 최고치가 2회 나타났으며, 제2일에도 제1일과 마찬가지로 18:00에 나타났고, 제3일에는 24:00에 나타나 제1일보다 제2일에는 최고치가 한 번 나타난 리듬을 보여주었고, 분비량은 2일에 감소하였다. 제3일에는 최고치가 8시간 지연된 나타난 리듬의 변화를 보여주었다. 최저치는 제1일, 제2일, 제3일 모두 24:00에 나타난 리듬을 보여주었다. 이상의 결과에서 실험군인 뇌손상 환자군에서는 뇌손상이 과도한 stress로 작용하여 환자의 free cortisol 분비량과 circadian 리듬에도 영향을 주는 것으로 나타났다. 그러므로 뇌손상환자를 간호하는 간호사는 스트레스상태인 것을 인지하여 환자 개개인에 필요한 간호를 해야 할 것으로 사료된다.

• Biomedical Science Letters
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• v.12 no.1
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• pp.53-56
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• 2006

The suprachiasmatic nucleus (SCN) of the anterior hypothalamus is the circadian pacemaker entrained to the 24-hr day by environmental time cues. Major circadian genes such as mPeriod ($mPer1{\sim}3$) and mCryptochrome ($mCry1{\sim}2$) are actively transcribed by the action of CLOCK/BMAL heterodimers, and in turn, these are being suppressed by the mPER/mCRY complex. In the study, the locomotor activity rhythms of mPer1 Knockout (KO) mice are measured, and the expression profiles of Heat Shock Protein 105kDa (HSP 105) genes in the SCN were measured by in situ hybridization. In agreement with previous reports, the locomotor activity rhythm of mPer1 KO mice was much shorter than that of wildtype. In addition, the total bout of activity of mPer1 KO was less in comparison to control mice. The expression of HSP 105 in the SCN of mPer1 KO mice was ranged from CT6 to CT22, with a peak level at CT14, implying that the gene are under the control of circadian clock. However, the expression of HSP 105 in the SCN of wildtype could not be detected in our study. Further analysis will reveal the direct or indirect regulation by mPer1 on the expression in the SCN and the role of the gene in the circadian clock.