• Development and Reproduction
• /
• v.17 no.3
• /
• pp.149-177
• /
• 2013

Living beings are surrounded by various changes exhibiting periodical rhythms in environment. The environmental changes are imprinted in organisms in various pattern. The phenomena are believed to match the external signal with organisms in order to increase their survival rate. The signals are categorized into circadian, seasonal, and annual cycles. Among the cycles, the circadian rhythm is regarded as the most important factor because its periodicity is in harmony with the levels of melatonin secreted from pineal gland. Melatonin is produced by the absence of light and its presence displays darkness. Melatonin plays various roles in creatures. Therefore, this review is to introduce the diverse potential ability of melatonin in manifold aspects in living organism.

• Sleep Medicine and Psychophysiology
• /
• v.4 no.2
• /
• pp.147-155
• /
• 1997

To assess the reliability of chronobiological models of sleep/wake regulation, it is necerssary that the models predict the data which has been studied in sleep research, and they should be generalized across all ages. To date, many adult human data on such models have accumulated, yet it is evident that a comprehensive theory of the biorhythmic aspects of sleep/wake states has not established. Circadian rhythms such as the time going to bed, sleep onset, slow wave sleep pressure, periodicity of REM sleep, daytime performance, and early evening alertness are resumed everyday. Even in adult humans, sleep is inherently polyphasic. In both the disentrained and entrained states, naps when allowed tend to recur in a temporally lawful manner. The monophasic sleep pattern of most industrial societies therefore appears to be purely of social origin. The endogenous biorhythmic nature of circasemidian sleep tendency is supported by the ubiquity of the phenomenon across all ages. The NREM/REM sleep cycle within sleep with its inherent physiological, endocrine, and neurochemical fluctuations represents the best-documented ultradian sleep rhythms. Also, a daytime ultradian variation in sleepiness with a periodicity similar to nocturnal NREM/REM cycle(BRAC hypothesis) is suggested. This review article provides a brief synoptic review of the evidences for circadian, circasemidian, and ultradian sleep/wake rhythms, and then the authour will suggest the issues which expedite fuller modeling of sleep/wake system, to be further discussed.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.50 no.5
• /
• pp.534-540
• /
• 2017

This study was conducted to determine the circadian rhythm and the effect of starvation for the health assessment of olive flounder Paralichthys olivaceus, reared under 12:12 LD (light:dark) cycle and fed 1% of their body weight once a day. The blood collection was implemented from 10 fish every 3 hours for a day, and analyzed to serval health parameters of the experimental fish. Plasma cortisol, glucose and total protein concentration reflected diel rhythms with high level of photophase and low level of scotophse despites of glutamic oxalacetic transaminase (GOT) and glutamic pyruvate transaminase (GPT) showing no rhythmicity, while electrolyte (sodium, potassium and chloride ion) concentrations arrived at the peak 18 hour and then slowly down. In the experiment of starvation, the result showed that there were no significant differences of the health parameters between the starved group and the fed. In short, our findings described the existence of circadian cortisol with glucose in flat fish, and indicated that the starvation does not almost affect the health of fish.

• Journal of Environmental Health Sciences
• /
• v.27 no.2
• /
• pp.10-16
• /
• 2001

To evaluate an effect of circadian variation on the xylene metabolizing enzyme activities, 50% m-xylene in olive oil(0.25 $m\ell$/100g body weight) was intraperitoneally administered to the rats every other day for 6 days both in the night; 24:00 and the day; 12:00. Then animals were sacrigiced at 8hr after last injection of m-xylene. Hepatic microsomal cytochrome p450 contents were more increased both in control and xylene treated rats of night phase than those of day phase. But the activity of hepatic alcohol dehydrogenase(ADH) in control of night phase showed the similar value with that in those of day phase and xylene treated rats of day phase showed an increasing tendency of hepatic ADH activity as those of night phase showing similar activity. Furthermore, control rats of night phase than those of day phase. And by xylene treatment, enzyme activities of rats of day phase were higher tendency in rats of control but those of night phase were somewhat inhibited. Besides, xylene-treated animals of night phase showed increasing tendency of urinary methylhippuric acid concentration compared with those of day phase. On the other hand, liver weight per body weight(%), hepatic lipid peroxide content and serum xanthine oxidase activity were higher in night phase. And the activities of hepatic oxygen free radical metabolizing enzymes such as xanthine oxidase, gluthathione S-transferase, and xylene-treated rats of night phase than those of day phase. In conclusion, it can be hypothesized on the basis of the results that the accumulation rate of m-xylene intermediate metabolite, i.e. m-methylbenzaldehyde in liver tissus may be higher in night phase than in day phase and it may be responsible for higher liver toxicity in bight phase than in day phase.

• Animal cells and systems
• /
• v.16 no.5
• /
• pp.357-365
• /
• 2012

We have examined the effect of circadian disturbances induced by night shifts (NSs) on the phenotypes of the tibiae and abdominal adipose tissues (ADTs) in a mouse model by using in vivo micro-computed tomography (micro-CT). We found that the volumes of total and visceral ADTs in the night-shifted group of mice were significantly larger (69 and 92%, respectively) than those in the control. The mean polar moment of inertia, cross-sectional thickness, and bone mineral density of the cortical bone in the night-shifted group of mice were less (13, 5, and 3%, respectively) than those in the control. Moreover, the volume and the thickness of growth plates (GPs) of the tibiae in the night-shifted mice were significantly smaller (22 and 20%, respectively) than those in the control. Taken together, our results indicate that disturbances in the mouse circadian rhythms induced by NSs affect the morphological characteristics of cortical bone, the volume and the thickness of GPs, and the volume of ADTs.

• Journal of the Ergonomics Society of Korea
• /
• v.19 no.3
• /
• pp.1-12
• /
• 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
• /
• v.50 no.5
• /
• pp.235-236
• /
• 2017

The circadian clock is an internal system that is synchronized by external stimuli, such as light and temperature, and influences various physiological and developmental processes in living organisms. In the model plant Arabidopsis, transcriptional, translational and post-translational processes are interlocked by feedback loops among morning- and evening-phased genes. In a post-translational loop, plant-specific single-gene encoded GIGANTEA (GI) stabilize the F-box protein ZEITLUPE (ZTL), driving the targeted-proteasomal degradation of TIMING OF CAB EXPRESSION 1 (TOC1) and PSEUDO-RESPONSE REGULATOR 5 (PRR5). Inherent to this, we demonstrate the novel biochemical function of GI as a chaperone and/or co-chaperone of Heat-Shock Protein 90 (HSP90). GI prevents ZTL degradation as a chaperone and facilitates ZTL maturation together with HSP90/HSP70, enhancing ZTL activity in vitro and in planta. GI is known to be involved in a wide range of physiology and development as well as abiotic stress responses in plants, but it could also interact with diverse client proteins to increase protein maturation. Our results provide evidence that GI helps proteostasis of ZTL by acting as a chaperone and a co-chaperone of HSP90 for proper functioning of the Arabidopsis circadian clock.

• Biomolecules & Therapeutics
• /
• v.19 no.3
• /
• pp.308-314
• /
• 2011

It has been shown that circadian genes not only play an important role on circadian rhythms, but also participate in other physiological and pathological activities, such as drug dependence, cancer development and radiation injury. The Per2, an indispensable component of the circadian clock, not only modulates circadian oscillations, but also regulates organic function. In the present study, we applied mPER2-upregulated NIH3T3 cells to reveal the relationship of mPer2 and the cells damaged by ultraviolet C (UVC). NIH3T3 cells at the peak of the expression of mPer2 induced by phorbol 12-myristate 13-acetate (PMA) demonstrated little damage by UVC evaluated by MTT assay, cell growth curves and cell colony-forming assay, compared with that at the nadir of the expression of mPer2. Overexpression of mPER2, accompanied p53 upregulated, also demonstrated protective effect on NIH3T3 cells damaged by UVC. These results suggest that mPer2 plays a protective effect on cells damaged by UVC, whose mechanism may be involved in upregulated p53.

• Journal of Korean Academy of Nursing
• /
• v.24 no.2
• /
• pp.175-189
• /
• 1994

This study examined the daily rhythmic patterns of mood in shift workers. Ten rotating shift nurses (shift worker group) were matched with ten non-rotating student nurses (non - shift worker group) working under the same conditions at University Hospital. The subjects completed the Mood Adjective Checkist (MAC) every two or three hours from 6AM to 9-11 PM for six consecutive days. The MAC was constructed by Mansour and conversed the mood factors of Anger - Depression. Happiness, Mental, and Social. These data were analyzed by using Cosinor method. The results are summarized as follows : 1. There was no difference in mean scores for Anger - Depression, Happiness, Mental, and Social mood rhythm between the shift workers and the non - shift workers. 2. There was no difference in the amplitude of Anger - Depression, Happiness and Social mood between the two groups, but the shift workers had a higher amplitude of Mental mood. 3. The acrophases of the Anger - Depression mood were between 1:28 and 2:05, and those of Happiness, Social, and Mental mood were between 12:5 and 15:03 for both groups. There were no differences between the groups. 4. The number of the subjects with statistically significant mean cosinor rhythms for Anger-De-pression and Mental moods were higher in the shift workers than in the non-shift workers, but there were no differences between the shift workers and the non-shift workers in those of Happiness and Mental mood. This study showed that the mod manifested circadian periodicities, and a rapidly rotating shift system did not changed the circadian rhythm of mood. It is expected that this study will facilitate a better understanding of circadian rhythm in mood in the shiftworkers.

• Journal of Life Science
• /
• v.27 no.10
• /
• pp.1225-1231
• /
• 2017

Disruptive expression patterns of the circadian clock genes are highly associated with many human diseases, including cancer. Cell cycle and proliferation is linked to a circadian rhythm; therefore, abnormal clock gene expression could result in tumorigenesis and malignant development. The molecular network of the circadian clock is based on transcriptional and translational feedback loops orchestrated by a variety of clock activators and clock repressors. The expression of 10~15% of the genome is controlled by the overall balance of circadian oscillation. Among the many clock genes, Period 1 (Per1) and Period 2 (Per2) are clock repressor genes that play an important role in the regulation of normal physiological rhythms. It has been reported that PER1 and PER2 are involved in the expression of cell cycle regulators including cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors. In addition, correlation of the down-regulation of PER1 and PER2 with development of many cancer types has been revealed. In this review, we focused on the molecular function of PER1 and PER2 in the circadian clock network and the transcriptional and translational targets of PER1 and PER2 involved in cell cycle and tumorigenesis. Moreover, we provide information suggesting that PER1 and PER2 could be promising therapeutic targets for cancer therapies and serve as potential prognostic markers for certain types of human cancers.