Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Wertheim cung cấp cho các bạn kiến thức về ngành y đề tài: Natural daylight restricted to twilights delays the timing of testicular regression but does not affect the timing of the daily activity rhythm of the house sparrow (Passer domesticus). | Journal of Circadian Rhythms BioMed Central Research Open Access Natural daylight restricted to twilights delays the timing of testicular regression but does not affect the timing of the daily activity rhythm of the house sparrow Passer domesticus Amit K Trivedi Sangeeta Rani and Vinod Kumar Address Department of Zoology University of Lucknow Lucknow 226 007 India Email Amit KTrivedi - amit_9trivedi@ Sangeeta Rani - sangeetarani7@ Vinod Kumar - drvkumar11@ Corresponding author Published 23 March 2006 Received 25 November 2005 Accepted 23 March 2006 Journal of Circadian Rhythms2006 4 5 doi 1740-3391-4-5 This article is available from http content 4 1 5 2006Trivedi et al licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License http licenses by which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. Abstract Background A stable and systematic daily change in light levels at dawn and dusk provides the most reliable indicator of the phase of the day. It is likely that organisms have evolved mechanisms to use these twilight transitions as the primary zeitgeber to adjust their circadian phases. In this study we investigated under natural illumination conditions the effects of daylight exposure restricted to twilights on the timing of testicular regression and locomotor activity of the house sparrow Passer domesticus which possesses a strongly self-sustaining circadian system. Methods and results Two experiments were performed on adult male house sparrows. Beginning in the third week of April the first experiment examined whether exposure to natural daylight only during twilights influenced the timing of testicular regression and concomitant changes in testosterone-dependent beak color of reproductively mature sparrows. Interestingly there was a .
