Phase Delay of the Rhythm of 6‐Sulphatoxy Melatonin Excretion by Artificial Light

Kennaway, David J.; Earl, C. R.; Shaw, Paul F.; Royles, P.; Carbone, Francesca; Webb, Helen

doi:10.1111/j.1600-079x.1987.tb00869.x

Cited by 21 publications

(9 citation statements)

References 8 publications

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“…served throughout the resetting trial showed daily phase shifts on the average of 1 to 3 h following each cycle of bright light exposure (Fig. 3), consistent with other one-pulse bright light studies (Kennaway et al, 1987;Bureswa et al, 1991;Laakso et al, 1993;Van Cauter et al, 1994;Hashimoto et al, 1996). The melatonin data from control subjects, all of whom remained in dim lighting and darkness, delayed on the average of -0.2 h per day, consistent with the daily delay expected due to the intrinsic period of the human circadian pacemaker observed in dim lighting conditions (Czeisler et al, 1995a).…”

Section: Response Of the Melatonin Rhythm Measured Throughout A Resetsupporting

confidence: 89%

Resetting the Melatonin Rhythm with Light in Humans

1997

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The endogenous circadian rhythm of melatonin in humans provides information regarding the resetting response of the human circadian timing system to changes in the light-dark (LD) cycle. Alterations in the LD cycle have both acute and chronic effects on the observed melatonin rhythm. Investigations to date have firmly established that the melatonin rhythm can be reentrained following an inversion of the LD cycle. Exposure to bright light and darkness given over a series of days can rapidly induce large-magnitude phase shifts of the melatonin rhythm. Even single pulses of bright light can shift the timing of the melatonin rhythm. Recent data have demonstrated that lower light intensities than originally believed are capable of resetting the melatonin rhythm and that stimulation of photopically sensitive photoreceptors (i.e., cones) is sufficient to reset the endogenous circadian melatonin rhythm. In addition to phase resetting, exposure to light of critical timing, strength, and duration can attenuate the amplitude of the endogenous circadian rhythm of melatonin. Measurement of melatonin throughout resetting trials provides a dynamic view of the resetting response of the human circadian pacemaker to light. Future studies of the melatonin rhythm in humans may further characterize the resetting response of the human circadian timing system to light.

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Section: Response Of the Melatonin Rhythm Measured Throughout A Resetsupporting

confidence: 89%

Resetting the Melatonin Rhythm with Light in Humans

1997

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“…These findings more clearly delineate the rate at which the circadian clock can be delayed in a practical protocol that could be used in the real world. Previous studies utilizing a single bright light pulse ending late at night with subjects waking at their habitual time (sleep episode truncated) have reported phase delays of about 1 hour [ 24 , 25 ]. Studies in which a single long duration bright light pulse (> 6 hours, up to ~10,000 lux) was paired with 2 days of a large delay (>8 hours) in the sleep/dark episode have reported phase delays of up to 3 hours [ 9 , 12 , 27 , 28 ].…”

Section: Discussionmentioning

confidence: 99%

Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color

Canton

Smith

Choi

et al. 2009

J Circadian Rhythms

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BackgroundLight exposure in the late evening and nighttime and a delay of the sleep/dark episode can phase delay the circadian clock. This study assessed the size of the phase delay produced by a single light pulse combined with a moderate delay of the sleep/dark episode for one day. Because iris color or race has been reported to influence light-induced melatonin suppression, and we have recently reported racial differences in free-running circadian period and circadian phase shifting in response to light pulses, we also tested for differences in the magnitude of the phase delay in subjects with blue and brown irises.MethodsSubjects (blue-eyed n = 7; brown eyed n = 6) maintained a regular sleep schedule for 1 week before coming to the laboratory for a baseline phase assessment, during which saliva was collected every 30 minutes to determine the time of the dim light melatonin onset (DLMO). Immediately following the baseline phase assessment, which ended 2 hours after baseline bedtime, subjects received a 2-hour bright light pulse (~4,000 lux). An 8-hour sleep episode followed the light pulse (i.e. was delayed 4 hours from baseline). A final phase assessment was conducted the subsequent night to determine the phase shift of the DLMO from the baseline to final phase assessment.Phase delays of the DLMO were compared in subjects with blue and brown irises. Iris color was also quantified from photographs using the three dimensions of red-green-blue color axes, as well as a lightness scale. These variables were correlated with phase shift of the DLMO, with the hypothesis that subjects with lighter irises would have larger phase delays.ResultsThe average phase delay of the DLMO was -1.3 ± 0.6 h, with a maximum delay of ~2 hours, and was similar for subjects with blue and brown irises. There were no significant correlations between any of the iris color variables and the magnitude of the phase delay.ConclusionA single 2-hour bright light pulse combined with a moderate delay of the sleep/dark episode delayed the circadian clock an average of ~1.5 hours. There was no evidence that iris color influenced the magnitude of the phase shift. Future studies are needed to replicate our findings that iris color does not impact the magnitude of light-induced circadian phase shifts, and that the previously reported differences may be due to race.

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“…Thus, modest (-30 percent) decreases in evening melatonin levels may reduce melatonin receptor activation, thereby altering functional melatonin responses. In humans, ambient light or magnetic field exposures that influence afternoon/evening melatonin levels also suppress or delay the onset of nocturnal melatonin production (6,(61)(62)(63)(64). The combined reduction of both daytime and nocturnal melatonin secretion would lead to reduced 24-hour melatonin secretion, which could alter immunologic (15,16), oncostatic (13)(14)(15), or antioxidant (17)(18)(19) processes influenced by melatonin.…”

Section: 4mentioning

confidence: 99%

Reduced Excretion of a Melatonin Metabolite in Workers Exposed to 60 Hz Magnetic Fields

Burch

Reif

Yost

et al. 1999

American Journal of Epidemiology

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The effects of occupational 60 Hz magnetic field and ambient light exposures on the pineal hormone, melatonin, were studied in 142 male electric utility workers in Colorado, 1995-1996. Melatonin was assessed by radioimmunoassay of its metabolite, 6-hydroxymelatonin sulfate (6-OHMS), in post-work shift urine samples. Personal magnetic field and light exposures were measured over 3 consecutive days using EMDEX C meters adapted with light sensors. Two independent components of magnetic field exposure, intensity (geometric time weighted average) and temporal stability (standardized rate of change metric or RCMS), were analyzed for their effects on creatinine-adjusted 6-OHMS concentrations (6-OHMS/cr) after adjustment for age, month, and light exposure. Geometric mean magnetic field exposures were not associated with 6-OHMS/cr excretion. Men in the highest quartile of temporally stable magnetic field exposure had lower 6-OHMS/cr concentrations on the second and third days compared with those in the lowest quartile. Light exposure modified the magnetic field effect. A progressive decrease in mean 6-OHMS/cr concentrations in response to temporally stable magnetic fields was observed in subjects with low workplace light exposures (predominantly office workers), whereas those with high ambient light exposure showed negligible magnetic field effects. Melatonin suppression may be useful for understanding human biologic responses to magnetic field exposures.

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Phase Delay of the Rhythm of 6‐Sulphatoxy Melatonin Excretion by Artificial Light

Cited by 21 publications

References 8 publications

Resetting the Melatonin Rhythm with Light in Humans

Resetting the Melatonin Rhythm with Light in Humans

Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color

Reduced Excretion of a Melatonin Metabolite in Workers Exposed to 60 Hz Magnetic Fields

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