Relationship between light intensity and phase resetting in a mammalian circadian system

Sharma, Vijay Kumar; Chandrashekaran, M. K.; Singaravel, Muniyandi; Subbaraj, R.

doi:10.1002/(sici)1097-010x(19990201)283:2<181::aid-jez8>3.0.co;2-i

Cited by 22 publications

(12 citation statements)

References 11 publications

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“…The shapes of the photic PRCs reported above are similar to those found for other insects and animals (7,8,16,17,22,23). Since the topological features of PRCs are crucial in determining the entrainability of circadian pacemakers to the daily light-dark cycle (9,10), significant differences in the magnitude of phase shifting between the two species of cockroaches reflect potential differences in their entrainment mechanisms and ability to adjust to various ecological situations.…”

Section: Discussionsupporting

confidence: 54%

“…Although Kennedy et al (29) found no significant relationship between period and the magnitude of phase shifts, in their study of Kowari, they found labile periodicities might affect the inherent inevitability of the biological clock to recognize local time (17). In a detailed analysis of the PRC in both species of the cockroaches we studied, the advance phase shifts were smaller than the phase delay shifts regardless of the length of the circadian period (Table 1).…”

Section: Discussionmentioning

confidence: 99%

“…PRCs help explain how the circadian pacemaker adjusts its phase to synchronize animals to its environment. The topological features of amplitude and shape of the PRC for a given zeitgeber stimulus reflect the degree of entrainability of a circadian rhythm (9,10,17,18). All photic and certain nonphotic signals constitute time cues from the environment that animals can use as zeitgebers to synchronize their endogenous clock with environmental cycles.…”

Section: Introductionmentioning

confidence: 98%

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ADJUSTABILITY OF THE CIRCADIAN CLOCK IN THE COCKROACHES: A COMPARATIVE STUDY OF TWO CLOSELY, RELATED SPECIES,BLATTELLA GERMANICAANDBLATTELLA BISIGNATA

Wei

Lee

2001

Chronobiology International

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A single 2h light pulse (250 lux) was given at various times to phase shift the locomotor circadian rhythm of two species of closely related cockroaches, Blattella bisignata and Blatella germanica. The phase-response curve (PRC) of both species showed a similar pattern. Phase delays and advances were induced by light pulse during the early and late subjective night, respectively, while no clear phase shifting was elicited during the subjective day. However, the magnitude of the phase delay (1.89h +/- 0.66h) and advance (0.69h +/- 0.36h) of B. bisignata was significantly larger than that of B. germanica (0.78h +/- 0.38h and 0.35h +/- 0.18h, respectively). This result indicates the superior adjustability of the circadian clock in B. bisignata. The period-response curve (PdRC) was also constructed for both species. Although both species did not show great flexibility in circadian period changes, the phase shifts were significantly correlated with the period changes in the advance zone of B. bisignata (r = 0.72, P < .1). This allowed the circadian clock of B. bisignata to display better entrainability since the phase advance adjustment was significantly more difficult than that of phase delay. The results indicate the overall adjustability of the circadian clock of B. germanica is inferior to that of B. bisignata. The significance of this finding is discussed from an ecological perspective.

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Section: Discussionsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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ADJUSTABILITY OF THE CIRCADIAN CLOCK IN THE COCKROACHES: A COMPARATIVE STUDY OF TWO CLOSELY, RELATED SPECIES,BLATTELLA GERMANICAANDBLATTELLA BISIGNATA

Wei

Lee

2001

Chronobiology International

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“…Rather than linearly rising to a log, power, or cube-root compression of illuminance, the human circadian system appears to follow logistic dynamics in response to light delivered during the late biological night, as has been demonstrated for light administered during the early biological night (36). Logistic dynamics have also been used to describe the photic dose response of the circadian timing system of nonhuman mammals (1,5,25,29,32). In response to 3 consecutive days of 5 h of experimental light exposure, the pacemaker has a half-maximum response that is achieved with illuminances of ϳ50 -160 lux (typical of indoor ambient illumination) and saturates at ϳ1,400 lux.…”

Section: Discussionmentioning

confidence: 99%

Temporal dynamics of late-night photic stimulation of the human circadian timing system

Zeitzer¹,

Khalsa²,

Boivin³

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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The light-dark cycle is the primary synchronizing factor that keeps the internal circadian pacemaker appropriately aligned with the environmental 24-h day. Although it is known that ocular light exposure can effectively shift the human circadian pacemaker and do so in an intensity-dependent manner, the curve that describes the relationship between light intensity and pacemaker response has not been fully characterized for light exposure in the late biological night. We exposed subjects to 3 consecutive days of 5 h of experimental light, centered 1.5 h after the timing of the fitted minimum of core body temperature, and show that such light can phase advance shift the human circadian pacemaker in an intensity-dependent manner, with a logistic model best describing the relationship between light intensity and phase shift. A similar sigmoidal relationship is also observed between light intensity and the suppression of plasma melatonin concentrations that occurs during the experimental light exposure. As with a simpler, 1-day light exposure during the early biological night, our data indicate that the human circadian pacemaker is highly sensitive even to typical room light intensities during the late biological night, with approximately 100 lux evoking half of the effects observed with light 10 times as bright.

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“…Broadband illumination-rodents Sharma et al [53] measured circadian phase shifts (advances and delays) of locomotor activity in nocturnal field mice exposed to various irradiances from diffused daylight. Irradiances as low as approximately 0.05 lW/cm 2 were sufficient to obtain measurable phase shifts, relative to darkness.…”

Section: Phase Shiftingmentioning

confidence: 99%

Of Mice and Women: Light as a Circadian Stimulus in Breast Cancer Research

Bullough

Rea

Figueiro

2006

Cancer Causes Control

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Two models of circadian phototransduction, for mouse and humans, have been published providing spectral sensitivities for these two species. Despite some methodological variations among the studies reviewed, the circadian systems of nocturnal rodents are approximately 10,000 times more sensitive to optical radiation than that of humans. Circadian effectiveness of different sources for both humans and nocturnal rodents are offered together with a scale relating their absolute sensitivities. Instruments calibrated in terms of conventional photometric units (e.g., lux) will not accurately characterize the circadian stimulus for either humans or rodents.

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Relationship between light intensity and phase resetting in a mammalian circadian system

Cited by 22 publications

References 11 publications

ADJUSTABILITY OF THE CIRCADIAN CLOCK IN THE COCKROACHES: A COMPARATIVE STUDY OF TWO CLOSELY, RELATED SPECIES,BLATTELLA GERMANICAANDBLATTELLA BISIGNATA

ADJUSTABILITY OF THE CIRCADIAN CLOCK IN THE COCKROACHES: A COMPARATIVE STUDY OF TWO CLOSELY, RELATED SPECIES,BLATTELLA GERMANICAANDBLATTELLA BISIGNATA

Temporal dynamics of late-night photic stimulation of the human circadian timing system

Of Mice and Women: Light as a Circadian Stimulus in Breast Cancer Research

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