• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.323-326
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• 1997

In this study, we investigated the circardian rhythm of complexity of cardiac dynamics in humans. Dynamic 24-hour electrocardiographic recordings were obtained from 30 healthy ambulant subjects aged 41 to 50 years. or each recordings, normalized low frequency (0.04-0.1 hertz) and high frequency (>0.15 hertz) component are calculated. our different indexes obtained from separate algorithms of nonlinear dynamics - approximate entropy, correlation dimension, Lyapunov exponent and fractal dimension - were calculated. During early morning, low frequency component rose rapidly with concomitant withdrawl of high frequency component. All the our indexes of nonlinear dynamics showed remarkably same circardian rhythm: an early morning dip preceded by a steep decline during late night, a gradual recovery during evening and a peak around midnight. These data indicate that the simultansous losses of all of the our different mechanisms of nonlinear control of heart rate during early morning, concomitent with the surge of symapathetic activity and reduction of vagal activity, may contribute to the increased incidence of cardiovascular events during morning hours.

• Sleep Medicine and Psychophysiology
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• v.1 no.1
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• pp.3-8
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• 1994

With the recent development of sleep medicine, insomnia has been perceived as a disease from a simple symptom. As there are various causes in a disease, proper treatment according to each cause is necessary for a more effective treatment In general, insomnia is classified into five categrories of physical, physiological, psychological, psychiatric and pharmacological aspects. However, such categorizations are often insufficient in treating insomnia. Furthermore understanding of the developmental mechanisms of insomnia is required. The function of sleep is developed and maintained through the balance of the reciprocal forces of sleep and arousal. These forces are contantly regulated by what is called a circadian rhythm. Sleep is induced by this rhythm which is affected by factors such as awakening time in the morning, amount of intellectual function, amount and time length of physical exercise and sunlight Insomnia could develop when this rhythm is delayed and leads to a "forbidden zone" which is a very difficult period for inducing sleep about two to four hours before the routine bedtime. Whereas sleep gradually develops in line with the circardian rhythm, arousal can occur very abruptly by any cause triggered by emotional discomfort or anxiety. Such characteristic and emotional factors as perfectionism, separation anxiety, secondary gain, insecurity, and negative cognition may provoke the inner anxiety and fear for insomnia, which can lead acute insomnia to a chronic one. As chronic insomnia is developed by multiple causes and factors, integrated approaches through analysis of above mentioned factors will be more effective in the treatment of insomnia than a simple administration of hypnotics.

• Toxicological Research
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• v.22 no.4
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• pp.411-416
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• 2006

This study was carried out to investigate the spaciotemporal plasticity of intergeniculate leaflet in postnatal mongolian gerbil using genetically modified pseudorabies virus recombinant, which was a kind of excellent neurotracer with the ability to transpass the neuronal synaptic cleft. In addition, we tried to evaluate the special role of intergeniculate leaflet as a signal controler of circardian rhythm by expression of various nourotransmitters in suprachiasrnatic nucleus. The PRV-BaBlu, a genetically modified strain of PRV-Bartha with lac-Z gene, was injected into vitreous body of postnatal mongolian gerbil, and immunostained. The PRV-Bablu infected the neurons in intergeniculate leaflet of postnatal mongolian gerbil, and the degree of viral infection in postnatal period of experimental animals had tendency to increase with time consuming. This results showed that the mutant PRV-Bar-tha strain with lac-Z gene, PRV-BaBlu, was a very excellent neurotracer to localize the retinogeniculate tract with infection of neurons in intergeniculate leaflet specially.

• Korean Journal of Clinical Laboratory Science
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• v.44 no.1
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• pp.31-37
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• 2012

Many mammals in temperate zones are affected by the distinctive changes of the four seasons in these zones. Their reproductive status is active in the summer climate and inactive during severe winter weather. The golden hamster (Mesocricetus auratus) is seasonal breeding animal whose sexual activities are regulated by photoperoidism. The reproduction and metabolism are activated by long summer days (LD) and inhibited by short winter days (SD). After several months of SD, animals become refractory to this inhibitory photoperiod and spontaneously revert to LD-like physiology. The suprachiasmatic nuclei (SCN) house the primary circadian oscillator in mammals. Seasonal changes in the photic input to this structure control many annual physiological rhythms via SCN-regulated pineal melatonin secretion, which provides an internal endocrine signal representing photoperiod. The aim of this study was to assess the variation in the morphology of the testis in relation to the natural photoperiod in male golden hamsters. The hamsters were castrated at different weeks (2, 5, 8, and 15). The cell numbers of tubules with spermatogonia (SG), spermatocyte (SC), spermatids (ST), and spermatozoa (SZ) were recorded in each sample. The results showed that testicular regression of golden hamsters occurred in the SD-treated animals. The present investigation determines that the effects of the photoperiod on the reproduction of male golden hamsters. It was also found that the circadian period increases the rate of reproductive inhibition in animals exposed to inhibitory photoperiods.

• The Korean Journal of Physiology and Pharmacology
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• v.5 no.4
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• pp.333-342
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• 2001

Adriamycin is a commonly used chemotherapeutic agent for cancer, including acute leukemia, lymphoma, and a number of solid human tumors. However, recent studies have recognized severe cardiotoxicity after an acute dose, which are likely the result of generation of free radicals and lipid peroxidation. Therefore, the clinical uses of adriamycin have been limited. Melatonin, the pineal gland hormone known for its ability to modulate circardian rhythm, has recently been studied in its several functions, including cancer growth inhibition, stimulating the immune system, and acting as an antioxidant and radical scavenging effects. In the present study, we evaluated the effect of melatonin administration on adriamycin-induced cardiotoxicity in rat. Heart slices were prepared using a Stadie-Riggs microtome for the measurement of malondialdehyde (MDA) content used as an index of lipid peroxidation and lactate dehydrogenase (LDH) release as an indicator of lethal cell injury. Serious adriamycin-induced lethality was observed in rat by a single intraperitoneal injection in a dose-dependent manner. A single injection of adriamycin (25 mg/kg, i.p.) induced a lethality rate of 86%, with melatonin (10 mg/kg s.c. for 6 days) treatment reducing the adriamycin-induced lethality rate to 20%. The severe body weight loss caused by adriamycin was also significantly attenuated by melatonin treatment. Treatment of melatonin marked reduced adriamycin-induced the levels of MDA formation and LDH release. A cell damage indicated by the loss of myofibrils, swelling of the mitochondria as well as cytoplasmic vacuolization was seen in adriamycin-treated group. Melatonin attenuated the adriamycin-induced structural alterations. These data provide evidence that melatonin prevents adriamycin-induced cardiotoxicity and might serve as a combination with adriamycin to limit free radical-mediated cardiotoxicity.