Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment
Groups of Syrian hamsters were exposed to LD cycles with twilight transitions and photoperiods simulating natural lighting conditions at the summer solstice (SS), equinox, and winter solstice (WS) at 41°N and at the winter solstice at the Arctic Circle (WS 66°N) but with daytime illuminance truncate...
Published in: | Journal of Biological Rhythms |
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Online Access: | http://dx.doi.org/10.1177/0748730404272907 http://journals.sagepub.com/doi/pdf/10.1177/0748730404272907 |
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crsagepubl:10.1177/0748730404272907 2024-06-23T07:50:48+00:00 Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment Boulos, Ziad Macchi, M. Mila 2005 http://dx.doi.org/10.1177/0748730404272907 http://journals.sagepub.com/doi/pdf/10.1177/0748730404272907 en eng SAGE Publications http://journals.sagepub.com/page/policies/text-and-data-mining-license Journal of Biological Rhythms volume 20, issue 2, page 132-144 ISSN 0748-7304 1552-4531 journal-article 2005 crsagepubl https://doi.org/10.1177/0748730404272907 2024-06-11T04:31:09Z Groups of Syrian hamsters were exposed to LD cycles with twilight transitions and photoperiods simulating natural lighting conditions at the summer solstice (SS), equinox, and winter solstice (WS) at 41°N and at the winter solstice at the Arctic Circle (WS 66°N) but with daytime illuminance truncatedat10 lux (LD-twilight). Separate groups were kept under matching rectangular cycles (LD-rectangular). The inclusion of twilights affected several circadian parameters in a season-and latitude-dependent manner. The most striking difference was in the timing of activity onsets, which followed dusk in the presence of twilights but were more closely related to dawn (lights-on) in their absence. Activity offsets and midpoints were also earlier in LD-twilight than in LD-rectangular, with the differences being most pronounced under WS 66°N. In LD-twilight, longer nights resulted in earlier offsets and midpoints, but in LD-rectangular, midpoints were later under long than under short nights while offsets did not vary significantly. In LD-twilight, activity duration (alpha) increased monotonically with increasing nighttime duration, but in LD-rectangular, alpha was shorter under WS 66°N than under WS conditions. These effects of season and latitude observed in LD-twilight were similar to those reported in animals exposed to natural illumination, while those observed in LD-rectangular differed in several respects. The presence of twilights also resulted in lower day-to-day variability in activity onset times (greater precision), supporting the earlier conclusion that twilights increase the strength of the LD zeitgeber. Free-running periods in constant darkness (DD) were shorter in LD-twilight than in LD-rectangular, especially under WS 66°N, raising the possibility that the effects of twilights on the timing of the entrained activity rhythm reflect their effects on the period of that rhythm. Increasing daytime illuminance to 100 lux (WS conditions only) resulted in earlier activity offsets and midpoints and a shorter alpha but ... Article in Journal/Newspaper Arctic SAGE Publications Arctic Journal of Biological Rhythms 20 2 132 144 |
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English |
description |
Groups of Syrian hamsters were exposed to LD cycles with twilight transitions and photoperiods simulating natural lighting conditions at the summer solstice (SS), equinox, and winter solstice (WS) at 41°N and at the winter solstice at the Arctic Circle (WS 66°N) but with daytime illuminance truncatedat10 lux (LD-twilight). Separate groups were kept under matching rectangular cycles (LD-rectangular). The inclusion of twilights affected several circadian parameters in a season-and latitude-dependent manner. The most striking difference was in the timing of activity onsets, which followed dusk in the presence of twilights but were more closely related to dawn (lights-on) in their absence. Activity offsets and midpoints were also earlier in LD-twilight than in LD-rectangular, with the differences being most pronounced under WS 66°N. In LD-twilight, longer nights resulted in earlier offsets and midpoints, but in LD-rectangular, midpoints were later under long than under short nights while offsets did not vary significantly. In LD-twilight, activity duration (alpha) increased monotonically with increasing nighttime duration, but in LD-rectangular, alpha was shorter under WS 66°N than under WS conditions. These effects of season and latitude observed in LD-twilight were similar to those reported in animals exposed to natural illumination, while those observed in LD-rectangular differed in several respects. The presence of twilights also resulted in lower day-to-day variability in activity onset times (greater precision), supporting the earlier conclusion that twilights increase the strength of the LD zeitgeber. Free-running periods in constant darkness (DD) were shorter in LD-twilight than in LD-rectangular, especially under WS 66°N, raising the possibility that the effects of twilights on the timing of the entrained activity rhythm reflect their effects on the period of that rhythm. Increasing daytime illuminance to 100 lux (WS conditions only) resulted in earlier activity offsets and midpoints and a shorter alpha but ... |
format |
Article in Journal/Newspaper |
author |
Boulos, Ziad Macchi, M. Mila |
spellingShingle |
Boulos, Ziad Macchi, M. Mila Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment |
author_facet |
Boulos, Ziad Macchi, M. Mila |
author_sort |
Boulos, Ziad |
title |
Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment |
title_short |
Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment |
title_full |
Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment |
title_fullStr |
Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment |
title_full_unstemmed |
Season- and Latitude-Dependent Effects of Simulated Twilights on Circadian Entrainment |
title_sort |
season- and latitude-dependent effects of simulated twilights on circadian entrainment |
publisher |
SAGE Publications |
publishDate |
2005 |
url |
http://dx.doi.org/10.1177/0748730404272907 http://journals.sagepub.com/doi/pdf/10.1177/0748730404272907 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
Journal of Biological Rhythms volume 20, issue 2, page 132-144 ISSN 0748-7304 1552-4531 |
op_rights |
http://journals.sagepub.com/page/policies/text-and-data-mining-license |
op_doi |
https://doi.org/10.1177/0748730404272907 |
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Journal of Biological Rhythms |
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20 |
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2 |
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132 |
op_container_end_page |
144 |
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1802641719920951296 |