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Michael Hastings, John S O’Neill, and Elizabeth S Maywood

rhythms, and then to apply this basic knowledge to understand what happens toour health and well-being when the body’s clockwork goes wrong. The suprachiasmatic nuclei(SCN)asa circadian clock It is perhaps unsurprising to observe

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Taira Wada, Yukiko Yamamoto, Yukiko Takasugi, Hirotake Ishii, Taketo Uchiyama, Kaori Saitoh, Masahiro Suzuki, Makoto Uchiyama, Hikari Yoshitane, Yoshitaka Fukada, and Shigeki Shimba

rhythm of behavior ( Moore & Eichler 1972 , Stephan & Zucker 1972 , Ralph et al. 1990 ). Peripheral tissues also have a circadian clock system, which can be driven autonomously ( Balsalobre et al. 1998 , Yamazaki et al. 2000 , Yoo et al. 2004

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S A Cavigelli, S L Monfort, T K Whitney, Y S Mechref, M Novotny, and M K McClintock

circadian glucocorticoid rhythm is altered in several pathological states; e.g. major depressive disorder ( Sachar et al. 1973 , Linkowski et al. 1985 , Pfohl et al. 1985 ), Alzheimer’s disease, sleep deprivation ( Spiegel et al. 1999 ), and normal

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Anjara Rabearivony, Huan Li, Shiyao Zhang, Siyu Chen, Xiaofei An, and Chang Liu

timing signals for living organisms on Earth. Consequently, according to these signals, the endogenous circadian rhythms within organisms are entrained to the solar day ( Pittendrich 1960 , Refinetti 2010 , Fonken et al. 2013 ). While the central

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Silvia Begliuomini, Elena Lenzi, Filippo Ninni, Elena Casarosa, Sara Merlini, Nicola Pluchino, Valeria Valentino, Stefano Luisi, Michele Luisi, and Andrea R Genazzani

there are no studies at present in the literature investigating a possible BDNF circadian rhythm in humans, we studied the BDNF levels throughout 24 h in healthy men, in order to detect the possible relative changes in plasma BDNF protein. Additionally

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Ingram JR, JN Crockford, and LR Matthews

Seasonal changes in the activity and responsiveness of the adrenal gland in red deer (Cervus elaphus) stags were quantified by measuring 24 h endogenous cortisol secretory profiles and plasma cortisol responses to either administration of exogenous ACTH or a standardised stressor during November (period of velvet growth), February (pre-rut), April (mid-rut) and July (post-rut) (southern hemisphere) using a remote blood sampling device (DracPac). Ultradian rhythms in the concentration of plasma cortisol were observed resulting from the episodic secretion of cortisol from the adrenal cortex at a mean rate of 0.8 pulses/h. Circadian rhythms in plasma cortisol concentrations were also found in 11 out of the 20 complete 24 h profiles (mean amplitude, 3.8+/-1.4 ng/ml). Seasonal rhythms in mean 24 h plasma cortisol concentrations and cortisol pulse parameters were also observed. Mean 24 h plasma cortisol concentrations were higher in November (12.5+/-1.0 ng/ml) than in February (6.3+/-1.0 ng/ml), April (4.0+/-1.0 ng/ml) or July (4.2+/-1. 0 ng/ml). Cortisol pulse height, nadir and amplitude were all significantly higher in November than at other times of the year (P<0.01). Peak cortisol concentrations following infusion of ACTH(1-24) (0.04 IU kg(-1)) were higher (P<0.05) in November (55.8+/-2.7 ng/ml) and lower (P<0.001) in April (33.7+/-1.8 ng/ml) than those in February and July (48.7+/-2.0 ng/ml and 45.4+/-2.0 ng/ml respectively). The area under the cortisol response curve was significantly smaller (P<0.05) in April (266.6+/-15.3 ng/ml/190 min) than at other times of the year (February, 366.1+/-15.3 ng/ml/190 min; July, 340.7+/-15.3 ng/ml/190 min and November, 387.8+/-21.2 ng/ml/190 min). These data demonstrate that the adrenal gland of the red deer stag exhibits ultradian, circadian and seasonal rhythms in activity, and that its responsiveness to ACTH varies with season. November, a period of reproductive quiescence in the southern hemisphere, with new antler growth and rapid weight gain, is associated with higher mean plasma cortisol concentrations and a greater responsiveness to exogenous ACTH. In contrast, the breeding season is associated with lower adrenal activity and responsiveness.

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Cátia F Gonçalves and Qing-Jun Meng

Introduction Circadian (from the Latin circa diem , meaning ‘about a day’) rhythms in behaviour and physiology are a hallmark of life on earth. The 24-h environmental cycles generated by the planet’s rotation around its axis have been wired

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Anthony H Tsang, Mariana Astiz, Maureen Friedrichs, and Henrik Oster

physiological target systems according to the time of day. It has long been appreciated that many hormones show circadian rhythms in the circulation ( Pincus et al . 1954 , Moore & Eichler 1972 ). Both central and peripheral tissue clocks impinge on such

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Henrik Oster

nocturnal light pollution and sleep-wake rhythm disruption in the case of the circadian clock. Ultimately, these perturbations synergize in their disruption of metabolism and energy homeostasis, arguably among the key medical challenges of the twenty

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Esther Isorna, Nuria de Pedro, Ana I Valenciano, Ángel L Alonso-Gómez, and María J Delgado

& Mistlberger 2013 ) and temperature cycles ( Buhr et al. 2010 , Poletini et al. 2015 , Schibler et al. 2015 ) are also important. These environmental factors are considered the ‘inputs’ of the circadian system, whereas the rhythms that are generated are