• Fisheries and Aquatic Sciences
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• v.20 no.8
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• pp.17.1-17.8
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• 2017

Somatostatin (SS) and growth hormone-releasing hormone (GHRH) are primary factors regulating growth hormone (GH) secretion in the pituitary. To date, it remains unknown how this rhythm is controlled endogenously, although there must be coordination of circadian manners. Melatonin was the main regulator in biological rhythms, and its secretion has fluctuation by photic information. But relationship between melatonin and growth-related genes (ghrh and ss) is unclear. We investigated circadian rhythms of melatonin secretion, ghrh and ss expressions, and correlation between melatonin with growth-related genes in tiger puffer Takifugu rubripes. The melatonin secretion showed nocturnal rhythms under light and dark (LD) conditions. In constant light (LL) condition, melatonin secretion has similar patterns with LD conditions. ss1 mRNA was high during scotophase under LD conditions. But ss1 rhythms disappeared in LL conditions. Ghrh appeared opposite expression compared with melatonin levels or ss1 expression under LD and LL. In the results of the melatonin injection, ghrh and ss1 showed no significant expression compared with control groups. These results suggested that melatonin and growth-related genes have daily or circadian rhythms in the tiger puffer. Further, we need to know mechanisms of each ss and ghrh gene regulation.

• Toxicological Research
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• v.16 no.2
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• pp.147-150
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• 2000

Melatonin plasma in Swallows exhibited circadian rhythmical secretions in the LD (Light and dark, 12：12) period with and without feeding. But their average difference between at CT6 (Circadian Time) and CT18 was 3.53 ng/$\textrm{m}{\ell}$ in LD period with feeding. on the other side 1.60 ng/$m\ell$ during without feeding. Melatonin concentration at CT6 without feeding incresed from 0.22 ng/$\textrm{m}{\ell}$ to 0.93 ng/$\textrm{m}{\ell}$. It is demonstrated that decresing melatonin secretion may reduce digestive function in order to ready for the migration. While the birds with feeding exhibited circadian rhythmical activity, their activity without feeding was durable. The concentrations of melatonin plasma by refeeding were 1.53 ng/$\textrm{m}{\ell}$ at CT6 and 6.07 ng/$\textrm{m}{\ell}$ at CT18. Melatonin plasma concentration in the night increased by more than ca. quadruple at day. This results suggest that melatonin regulates metabolism for the return to the normal metabolism condition after migration. After 3 days refeeding melatonin was secreted circadian rhythmically same as the secretions with feeding at beginning.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.05a
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• pp.160-160
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• 2003

Plasma melatonin in the seasonal light-period is circadian rhythmically secreted. Maximal secretion showed at 14 o'clock in summer- and winter-like period, but minimal secretion showed at 5 o'clock in summer-like period and at 8 in winter-like period. These times of minimal secretions were at the beginning of light period. Plasma melatonin in the light period is secreted 62.5% more than in the dark period in summer-like period and 45.9% more in winter-like period. Total plasma melatonin in winter-like period is secreted 56.5% more than in summer-like period. The weights of testis(-20.8%) and body(-7.1%) were reduced in the winter-like period. By the increase of plasma melatonin in mice, body- and testis-weights are decreased, on the contrary by the decrease of plasma melatonin in mice, body and testis weights are increased. In view of the results so far achieved melatonin changes on the body weight and reproductive organ in mice. It is presumed that melatonin effects on the metabolism and sex hormone.

• Environmental Analysis Health and Toxicology
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• v.18 no.1
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• pp.57-61
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• 2003

Plasma melatonin in the seasonal light-period is circadian rhythmically secreted. Maximal secretion showed at 14 o'clock in summer- and winter-like period, but minimal secretion showed at 5 o'clock in summer-like period and at 8 in winter-like period. These times of minimal secretions were at the beginning of light period. Plasma melatonin in the light period is secreted 62.5％ more than in the dark period in summer- like period and 45.9％ more in winter- like period. Total plasma melatonin in winter-like period is secreted 56.5％ more than in summer-like period. The weights of testis (-20.8％) and body (-7.1％) were reduced in the winter-like period. By the increase of plasma melatonin in mice, body - and testis -weights are decreased, on the contrary by the decrease of plasma melatonin in mice, body and testis weights are increased. In view of the results so far achieved melatonin changes on the body weight and reproductive organ in mice. It is presumed that melatonin effects on the metabolism and sex hormone.

• International Journal of Oral Biology
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• v.44 no.2
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• pp.50-54
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• 2019

Melatonin is a neurotransmitter that modulates various physiological phenomena including regulation and maintenance of the circadian rhythm. Nicotinic acetylcholine receptors (nAChRs) play an important role in oral functions including orofacial muscle contraction, salivary secretion, and tooth development. However, knowledge regarding physiological crosstalk between melatonin and nAChRs is limited. In the present study, the melatonin-mediated modulation of nAChR functions using bovine adrenal chromaffin cells, a representative model for the study of nAChRs, was investigated. Melatonin inhibited the nicotinic agonist dimethylphenylpiperazinium (DMPP) iodide-induced cytosolic free $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) increase and norepinephrine secretion in a concentration-dependent manner. The inhibitory effect of melatonin on the DMPP-induced $[Ca^{2+}]_i$ increase was observed when the melatonin treatment was performed simultaneously with DMPP. The results indicate that melatonin inhibits nAChR functions in both peripheral and central nervous systems.

• Science of Emotion and Sensibility
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• v.20 no.4
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• pp.135-142
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• 2017

In the present study, we investigated the physiological effects of smartphone use at night when the display luminance and white balance were differently manipulated. Two levels of luminance and two types of white balance were combined to form four types of displays. Subjects were instructed to use smartphones between 23:00 to 01:00 twice a week for two weeks, and for each trial, subjects were given one of the four display types. Melatonin concentration in the saliva, body temperature and heart rate were measured before and after each experiment. The experimental result showed that the low luminance display supported melatonin secretion and thermoregulation compared to the high luminance display. With regard to the white balance, higher melatonin level was observed when using the display that filtered blue light. The low luminance display together with yellowish tint best supported restful sleep at night in terms of every physiological response. This study collectively demonstrates that bright and blue light emitted from smartphone displays adversely affect melatonin secretion, body temperature, and heart rate, and therefore, suggests the use of a display with low luminance or a display that filters blue light for a restful sleep at night.

• Korean Journal of Food Science and Technology
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• v.42 no.2
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• pp.142-146
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• 2010

Relatively large amounts of GABA can be produced by the fermentation of rice bran. Therefore, this study was conducted to investigate the effects of GABA on the secretion of melatonin and serotonin for the development of a sleep inductive compound. The secretion levels of melatonin and serotonin from mice were found to be $3.425{\pm}0.182\;pg/mL$ and $5.37{\pm}0.963\;ng/mL$, respectively, in response to feeding 120 mg/mL of GABA while they were $2.607{\pm}0.41\;pg/mL$ in the control. The secretion of both melatonin and serotonin was increased up to the 13.51% and 34.99%, respectively, when compared to the negative control. However, the feeding of milk alone did not have a great effect on the melatonin and serotonin secretions. Conversely, feeding of milk with GABA enhanced the secretion of serotonin. The amounts of both melatonin and serotonin secreted increased with respect to the increase in GABA concentrations during feeding. Interestingly, the induction level of melatonin was relatively higher than that of serotonin in response to feeding 120 mg/mL of GABA. This is the first study to report that GABA has an ability to induce sleep related hormones in mice; therefore, it has the potential for use as a natural sleep aid.

• Fashion & Textile Research Journal
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• v.6 no.5
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• pp.613-617
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• 2004

The intent of this study was to determine whether different light exposure could modify the clothing behavior in the evening cold environment or not. Nine female subjects volunteered to this study. In a bright light or a dim light condition, light intensity was controlled 3000 lx or 10 lx respectively. Subjects were introduced to wear various kinds of garments whenever they need to feel comfortable as the room temperature began to decrease. The room temperature was lowered from $30^{\circ}C$ to $15^{\circ}C$ for one hour (21:00 h~22:00 h) and maintained at $15^{\circ}C$ for additional one hour (22:00 h~23:00 h). Subjects stayed in chamber from 08:00 to the next day 07:00. Clothing behavior, core temperature, subjective temperature sensation and melatonin secretion were measured. Most subjects put on the clothing more quickly and more thickerly in the bright light rather than in the dim light condition. The fall of core temperature during night was significantly less under the bright light in the late afternoon, suggesting that the set-point of core temperature has been set at a higher level during the evening and the night, being supported by the less amount of melatonin secretion. Thus, it is concluded that the quicker dressing behavior with thicker clothing in the "Bright" condition is advantageous in evening cold exposure, since it enables the core temperature to reach its set-point value more easily.

• Biomolecules & Therapeutics
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• v.28 no.3
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• pp.240-249
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• 2020

Despite the therapeutic effect of mesenchymal stem cells (MSCs) in ischemic diseases, pathophysiological conditions, including hypoxia, limited nutrient availability, and oxidative stress restrict their potential. To address this issue, we investigated the effect of melatonin on the bioactivities of MSCs. Treatment of MSCs with melatonin increased the expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α). Melatonin treatment enhanced mitochondrial oxidative phosphorylation in MSCs in a PGC-1α-dependent manner. Melatonin-mediated PGC-1α expression enhanced the proliferative potential of MSCs through regulation of cell cycle-associated protein activity. In addition, melatonin promoted the angiogenic ability of MSCs, including migration and invasion abilities and secretion of angiogenic cytokines by increasing PGC-1α expression. In a murine hindlimb ischemia model, the survival of transplanted melatonin-treated MSCs was significantly increased in the ischemic tissues, resulting in improvement of functional recovery, such as blood perfusion, limb salvage, neovascularization, and protection against necrosis and fibrosis. These findings indicate that the therapeutic effect of melatonin-treated MSCs in ischemic diseases is mediated via regulation of PGC-1α level. This study suggests that melatonin-induced PGC-1α might serve as a novel target for MSC-based therapy of ischemic diseases, and melatonin-treated MSCs could be used as an effective cell-based therapeutic option for patients with ischemic diseases.

• Sleep Medicine and Psychophysiology
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• v.22 no.1
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• pp.5-10
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• 2015

The secretion of melatonin exhibits a circadian rhythm entrained with the sleep-wake cycle. An alteration of this secretory rhythm has been found in various psychiatric disorders. This review summarizes the regulation of melatonin and its relationship to the circadian rhythm, major depressive disorder, bipolar disorder, seasonal affective disorder, Alzheimer's disease and autism. The review also looks at the effect of melatonin and melatonin agonist on sleep and symptoms of depression, bipolar disorder and seasonal affective disorder. In Alzheimer's disease, the circadian rhythm alterations are associated with the change of melatonin levels and melatonin receptors. It has been reported that melatonin and melatonin synthetic enzyme levels decrease in autism spectrum disorder.