• Sleep Medicine and Psychophysiology
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• v.21 no.2
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• pp.51-60
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• 2014

A 'circadian rhythm' is a self-sustained biological rhythm (cycle) that repeats itself approximately every 24 hours. Circadian rhythms are generated by an internal clock, or pacemaker, and persist even in the absence of environmental time cues, collectively termed 'zeitgebers.' Although organisms generate circadian rhythms internally, they are entrained by environmental stimuli, particularly the light-dark cycle. Measurement of the endogenous melatonin rhythm provides relatively reliable surrogate way of assessing the timing of the internal circadian clock. Also, core body temperature and cortisol can be used as markers of circadian rhythms. The sleep-wake cycle, body temperature, and melatonin rhythm have a stable internal phase relationship in humans and other diurnal species. They play an important role in controlling daily behavioral rhythms including task performance, blood pressure, and synthesis and secretion of several hormones. In this review, we address not only the properties, methods of measurement, and markers of circadian rhythms, but also the physiological and psychological importance of human circadian rhythms.

• Sleep Medicine and Psychophysiology
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• v.16 no.1
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• pp.5-9
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• 2009

Relatively little is known about the neurobiology of insomnia, despite its wide prevalence and broad medical impact. Although much is still to be learned about the pathophysiology of the disorder, identification, systematic assessment, and appropriate treatment are clearly beneficial to patients. Recent research, using quantitative EEG, polysomnography (PSG), multiple sleep latency test (MSLT) and neuroimaging techniques, suggests that some broad areas can be identified as possible pathophysiological models. Sleep-wake homeostat model hypothesizes a failure in homeostatic regulation of sleep, an attenuated increase in sleep drive with time awake, and/or defective sensing of sleep need. Circadian clock model hypothesizes a dysfunctional circadian clock, resulting in changes in the timing of sleep-wake propensity that are incompatible with normal sleep. Intrinsic sleep-wake state mechanism model suggests that abnormal function of insomnia comprises the systems responsible for expression of the sleep states themselves. Extrinsic over-ride mechanism (stress-response) model suggests that insomnia reflects the consequences of overactivity of one of the systems considered "extrinsic" to normal sleep-wake control. Many current therapies for insomnia are based on these physiological models. Several attempts have been made to create a physiological model that would explain this disorder and could be used as a foundation for treatment. However, it appeared that no model can fully explain and clarify all aspects of insomnia. Future research should be necessary to expand our knowledge on the biological dimensions of insomnia.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.70-76
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• 2005

It is known that natural awakening of us in the morning is due to stimulation of the reticular activation system through biological clock in the suprachiasmatic nucleus of hypothalamus by the morning sunlight. If we sleep at dark rooms without windows and so without morning sunlight, thus, it is not easy fur us to get up refreshingly in the morning. In this paper, we propose an automatic sunrise household lighting system that helps us fer getting up cheerfully in the morning even if we sleep in dark rooms without morning sunlight. The proposed lighting system is an embedded system that turns automatically on the electric lamp and makes it brighter and brighter coincidently with the actual sunrise. The proposed system is composed of a PIC microcontroller with flash memory, a real-time clock IC, a D/A converter, an amplifier, a dimmer unit, a light bulb, a display panel and a keyboard. The validity of the proposed intelligent lighting system is demonstrated via a prototype production and experimentation.

• Molecules and Cells
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• v.26 no.1
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• pp.53-60
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• 2008

We characterized the human endogenous retrovirus (HERV-W) family in humans and primates. In silico expression data indicated that 22 complete HERV-W families from human chromosomes 1-3, 5-8, 10-12, 15, 19, and X are randomly expressed in various tissues. Quantitative real-time RT-PCR analysis of the HERV-W env gene derived from human chromosome 7q21.2 indicated predominant expression in the human placenta. Several copies of repeat sequences (SINE, LINE, LTR, simple repeat) were detected within the complete or processed pseudo HERV-W of the human, chimpanzee, and rhesus monkey. Compared to other regions (5'LTR, Gag, Gag-Pol, Env, 3'LTR), the repeat family has been mainly integrated into the region spanning the 5'LTRs of Gag (1398 bp) and Pol (3242 bp). FISH detected the HERV-W probe (fosWE1) derived from a gorilla fosmid library in the metaphase chromosomes of all primates (five hominoids, three Old World monkeys, two New World monkeys, and one prosimian), but not in Tupaia. This finding was supported by molecular clock and phylogeny data using the divergence values of the complete HERV-W LTR elements. The data suggested that the HERV-W family was integrated into the primate genome approximately 63 million years (Myr) ago, and evolved independently during the course of primate radiation.

• Journal of Photoscience
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• v.9 no.2
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• pp.29-32
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• 2002

Studies till date suggest the existence of a fetal biological clock in suprachiasmatic nuclei entrained by the circadian signal from mother. Melatonin from maternal pineal gland reaches to the fetus by crossing every biological barrier including placenta, hence fetuses were exposed to similar melatonin variation as their mother. Experimental modulations of maternal pineal gland activity of pregnant females either by exposing the them to different photoperiodic schedules or by exogenous melatonin treatments till the date of parturition, regulated the fetal plasma level of melatonin, thereby the prenatal (fetal) growth and development. This clearly suggests the maternal transport of melatonin to their fetus through placenta since fetal retina-hypothalamic tract was incomplete. An extension of experimental schedules till 60 days of post-partum period regulated the neonatal pineal gland activity and gonadal maturation along with their plasma levels of melatonin and sex steroids suggesting clearly the phenomenon of maternal transfer of melatonin to their young ones during the post-natal period, when the neonates were solely dependent on the mother's milk for their nutrition and energetic demands. On the basis of above observations we may suggest that the maternal pineal gland activity regulate the prenatal development by passing its melatonin to fetus via placenta and post-natal growth and sexual maturation by passing maternal melatonin to neonates via milk. Hence, the photoperiod perceived by mother is translated into the maternal plasma level of melatonin which not only regulates the prenatal but also the post-natal growth and sexual maturation of neonates.

• Journal of Applied Biological Chemistry
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• v.53 no.3
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• pp.121-125
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• 2010

In the past 10 years, a lot of plant circadian rhythm researches have published in molecular biology and biochemistry. We discussed with published molecular studies of circadian clock and rhythmic genes in Arabidopsis, rice and algae. However past this studies are not sufficient to explain the whole rhythmic metabolism. Recently many researchers have concerned post-transcriptional, translational and post-translational modification of rhythmic proteins. From the view point of the high-throughput study, we could suggest the proteomic analysis with 2-DE gel electrophoresis and MS/MS techniques for the identification of modified proteins.

• Journal of Microbiology and Biotechnology
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• v.10 no.2
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• pp.169-175
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• 2000

The filamentous soil bacterium Streptomyces coelicolor is known to produce four distinct antibiotics. The simultaneous global regulation for the biosynthesis of those four antibiotics was previously confirmed by absA and absB mutations that blocked all four antibiotics' biosynthesis without influencing their morphological differentiation. To study the complex regulatory cascade that controls the secondary metabolism in Streptomyces, a new abs-like mutation was characterized. namely absR, which is slightly leaky on a complete R2YE medium, yet tight on a minimal medium. A genetic analysis of the absR locus indicated that it is located at 10 o'clock on the genetic map, near the site of absA. A cloned copy of the absA gene that encoded bacterial two-component regulatory kinases did not restore antibiotic biosyntheis to the absR mutant. Accordingly, it is proposed that absR is another abs-type mutation which is less tight than the previously identified absA or absB mutations income medium conditions, and can be used to characterize another global regulatory gene for secondary metabolete formation in S. coelicolor.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.6
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• pp.658-663
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• 2015

In the previous work, we have proposed an integrate-and-fire neuron circuit and synaptic device based on the floating body MOSFET [1-3]. Integrate-and-Fire(I&F) neuron circuit emulates the biological neuron characteristics such as integration, threshold triggering, output generation, refractory period using floating body MOSFET. The synaptic device has short-term and long-term memory in a single silicon device. In this paper, we connect the neuron circuit and the synaptic device using current mirror circuit for summation of post synaptic pulses. We emulate spike-timing-dependent-plasticity (STDP) characteristics of the synapse using feedback voltage without controller or clock. Using memory device in the logic circuit, we can emulate biological synapse and neuron with a small number of devices.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.12
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• pp.1022-1032
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• 1989

King Sejong's Striking Clepsydra was an elaborate timekeeping and annunciating system incorporating biological automata capable of annunciating hours, intervals and night-watches based on Shou-shih calindrical systems automatically. In this paper the author has studied the original manuscripts on the Striking Clepsydra [Sejong sillock, 65: 1a-3b ff` 16th year, 7th month(1434)] from the technical point of view undertaking a close analysis of this monumental clock and aiming to our modern understanding of the full degree of delicate mechanisms and sophisticated controls built into the night-watch and division announcing clockwork(jackwork). Based on the input/output model, timekeeping, ball-rack, ball-relay, and audible time-indicating mechanisms were synthesized reconstructing night-watch annunciating systems. It revealed that the night-watch and division announcing processes were entirely renewed automatically. Historical and philological data concerning the improvements of the proposed model were discussed.

• Journal of Biomedical Engineering Research
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• v.9 no.1
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• pp.79-86
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• 1988

This paper describes the design of a hardware systenl for ECG feature extraction based on pipeline processor consistinsf of three microcomputers. ECG data is acquisited by 12 bit A/D converter with hardware QRS triggered detector. Four diagnostic parameters parameters-heart rate, morPhology, axis, and 57 segment-are used for the classification and the diagnosis of arrhythmia. The functions of the main CPU were distributed and processed with three microcomputers. Therefore the effective data process and the real time process using microcomputer can be obtained. The interconnection structure consisting of two common memory units is designed to decrease the delay time caused by data transfer between processors and designed by which the delay time can be taken Loye of one clock period.