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Author

Katsuhisa Uchida

Bio: Katsuhisa Uchida is an academic researcher from Hamamatsu University School of Medicine. The author has contributed to research in topics: Melatonin & Circadian rhythm. The author has an hindex of 10, co-authored 14 publications receiving 444 citations.
Topics: Melatonin, Circadian rhythm, Dementia, Lamprey, Erg

Papers
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Journal ArticleDOI
TL;DR: The results suggest that the probability of absent melatonin rhythm is higher in demented patients compared with subjects without dementia, however, a lack of melatonin Rhythm is not always associated with symptomatic rhythm disorders.

139 citations

Journal ArticleDOI
TL;DR: The high levels of melatonin in the daytime associated with a lack of response to light exposure in AD patients may be due to the neurodegenerative process of this disease.

117 citations

Journal ArticleDOI
TL;DR: The results indicate that the pineal organ of the lamprey is a photoreceptive organ responsible for synchronizing locomotor activity to LD cycle, and appears to function as an oscillator, or as one of the oscillators, for the circadian locomotor rhythm of lampreys.
Abstract: Locomotor activity of the river lamprey, Lampetra japonica, was investigated under a light-dark (LD 12∶12) cycle and under continuous dark conditions. Intact lampreys were entrained to the light:dark cycle. They were active mainly in the early half of the dark period and inactive in light period. The light:dark entrainment continued in 72.7% of lampreys after the removal of bilateral eyes, but additional pinealectomy made the entrainment disappear in all lampreys. When lampreys were pinealectomized with their eyes intact, light: dark entrainment was abolished in most cases. The results indicate that the pineal organ of the lamprey is a photoreceptive organ responsible for synchronizing locomotor activity to LD cycle. Under continuous dark conditions, the locomotor activity began to free-run with a period of 21.3 ± 0.9 h (mean ± SD, n = 53). This circadian rhythmicity was not affected by the removal of lateral eyes but was abolished by pinealectomy. The pineal organ appears to function as an oscillator, or as one of the oscillators, for the circadian locomotor rhythm of lampreys.

41 citations

Journal ArticleDOI
TL;DR: It is suggested that the pattern ofmelatonin rhythm alters significantly without clear clinical symptoms in the process of senescence, suggesting that the off-set time of melatonin secretion advances with aging.
Abstract: The daily profile of serum level of melatonin was studied in 10 young and 13 elderly subjects. All of the subjects were physically and psychiatrically healthy and did not have any clinical symptoms re

26 citations

Journal ArticleDOI
TL;DR: The results indicate that, in cultures, the melatonin secretion rhythm in the pineal organ of the lamprey is both light- and temperature-sensitive, and that in vivo, themelatonin rhythm is not the critical factor maintaining the locomotor activity rhythm of the Lamprey.
Abstract: To identify the characteristics of the oscillator located in the pineal organ, we examined the effects of temperature and light on melatonin secretion rhythm using pineal organs in cultures. At 20 degrees C, the melatonin rhythm was obvious: low secretion during the daytime and high during the nighttime. When the temperature was lowered from 20 to 10 degrees C, the melatonin rhythm disappeared. When the temperature was returned from 10 to 20 degrees C, the rhythm quickly reappeared. The plasma melatonin level was measured in living lampreys kept at 7 degrees C to establish the melatonin profile at low temperature in vivo: secretion was not significantly different between daytime and nighttime. Under continuous light conditions, the melatonin elevation normally seen during the subjective night became obscure after 72 h. When the LD cycle was shifted by 6 h (phase-advanced or phase-delayed), the melatonin rhythm shifted to remain in the same phase relation to the LD cycle. This re-synchronization took several LD cycles. The results indicate that, in cultures, the melatonin secretion rhythm in the pineal organ of the lamprey is both light- and temperature-sensitive, and that in vivo, the melatonin rhythm is not the critical factor maintaining the locomotor activity rhythm of the lamprey. The role of the pineal organ and melatonin in the circadian organization of the lamprey is discussed.

25 citations


Cited by
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Journal ArticleDOI
TL;DR: There are a number of ways in which a clinical diagnosis of dementia of the Alzheimer type can be made – the application of clinical criteria is the commonest but ancillary techniques such as neuroima are also used.
Abstract: There are a number of ways in which a clinical diagnosis of dementia of the Alzheimer type can be made – the application of clinical criteria is the commonest but ancillary techniques such as neuroima

1,514 citations

Journal ArticleDOI
22 Jul 2004-Nature
TL;DR: Using microarray analysis, it is shown that heterochromatin in Arabidopsis is determined by transposable elements and related tandem repeats, under the control of the chromatin remodelling ATPase DDM1 (Decrease in DNA Methylation 1).
Abstract: Heterochromatin has been defined as deeply staining chromosomal material that remains condensed in interphase, whereas euchromatin undergoes de-condensation. Heterochromatin is found near centromeres and telomeres, but interstitial sites of heterochromatin (knobs) are common in plant genomes and were first described in maize. These regions are repetitive and late-replicating. In Drosophila, heterochromatin influences gene expression, a heterochromatin phenomenon called position effect variegation. Similarities between position effect variegation in Drosophila and gene silencing in maize mediated by "controlling elements" (that is, transposable elements) led in part to the proposal that heterochromatin is composed of transposable elements, and that such elements scattered throughout the genome might regulate development. Using microarray analysis, we show that heterochromatin in Arabidopsis is determined by transposable elements and related tandem repeats, under the control of the chromatin remodelling ATPase DDM1 (Decrease in DNA Methylation 1). Small interfering RNAs (siRNAs) correspond to these sequences, suggesting a role in guiding DDM1. We also show that transposable elements can regulate genes epigenetically, but only when inserted within or very close to them. This probably accounts for the regulation by DDM1 and the DNA methyltransferase MET1 of the euchromatic, imprinted gene FWA, as its promoter is provided by transposable-element-derived tandem repeats that are associated with siRNAs.

1,199 citations

Journal ArticleDOI
TL;DR: Control of electron flux, prevention of bottlenecks in the respiratory chain and electron leakage contribute to the avoidance of damage by free radicals and seem to be important in neuroprotection, inflammatory diseases and, presumably, aging.

709 citations

Journal ArticleDOI
TL;DR: A rapidly expanding literature attests to the involvement of melatonin in immune function, with high levels promoting and low levels suppressing a number of immune system parameters.

492 citations

Journal ArticleDOI
25 Nov 2016-Science
TL;DR: In this article, the authors explore potential cellular and molecular mechanisms linking circadian dysfunction and sleep loss to neurodegenerative diseases, with a focus on Alzheimer's disease, and discuss therapeutic implications.
Abstract: Disruptions of normal circadian rhythms and sleep cycles are consequences of aging and can profoundly affect health. Accumulating evidence indicates that circadian and sleep disturbances, which have long been considered symptoms of many neurodegenerative conditions, may actually drive pathogenesis early in the course of these diseases. In this Review, we explore potential cellular and molecular mechanisms linking circadian dysfunction and sleep loss to neurodegenerative diseases, with a focus on Alzheimer’s disease. We examine the interplay between central and peripheral circadian rhythms, circadian clock gene function, and sleep in maintaining brain homeostasis, and discuss therapeutic implications. The circadian clock and sleep can influence a number of key processes involved in neurodegeneration, suggesting that these systems might be manipulated to promote healthy brain aging.

484 citations