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Author Gorman, M. R.; Elliott, J. A. url  doi
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  Title Dim nocturnal illumination alters coupling of circadian pacemakers in Siberian hamsters, Phodopus sungorus Type Journal Article
  Year 2004 Publication Journal of Comparative Physiology A Abbreviated Journal (up) Comp Physiol A  
  Volume 190 Issue 8 Pages 631-  
  Keywords animals; rodents; seasonal timing  
  Abstract The circadian pacemaker of mammals comprises multiple oscillators that may adopt different phase relationships to determine properties of the coupled system. The effect of nocturnal illumination comparable to dim moonlight was assessed in male Siberian hamsters exposed to two re-entrainment paradigms believed to require changes in the phase relationship of underlying component oscillators. In experiment 1, hamsters were exposed to a 24-h light-dark-light-dark cycle previously shown to split circadian rhythms into two components such that activity is divided between the two daily dark periods. Hamsters exposed to dim illumination (<0.020 lx) during each scotophase were more likely to exhibit split rhythms compared to hamsters exposed to completely dark scotophases. In experiment 2, hamsters were transferred to winter photoperiods (10 h light, 14 h dark) from two different longer daylengths (14 h or 18 h light daily) in the presence or absence of dim nighttime lighting. Dim nocturnal illumination markedly accelerated adoption of the winter phenotype as reflected in the expansion of activity duration, gonadal regression and weight loss. The two experiments demonstrate substantial efficacy of light intensities generally viewed as below the threshold of circadian systems. Light may act on oscillator coupling through rod-dependent mechanisms.  
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  Call Number LoNNe @ schroer @ Serial 1590  
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Author Dauchy, R T; Wren, M A; Dauchy, E M; Hoffman, A E; Hanifin, J P; Warfield, B; Jablonski, M R; Brainard, G C; Hill, S M; Mao, L; Dobek, G L; Dupepe, L M; Blask, D E url  openurl
  Title The influence of red light exposure at night on circadian metabolism and physiology in Sprague-Dawley rats Type Journal Article
  Year 2015 Publication Journal of the American Association for Laboratory Animal Science Abbreviated Journal (up) JAALAS  
  Volume 54 Issue 1 Pages 40-50  
  Keywords animals; rodents; Circadian Rhythm; Light wavelength  
  Abstract Early studies on rodents showed that short-term exposure to high-intensity light (> 70 lx) above 600 nm (red-appearing) influences circadian neuroendocrine and metabolic physiology. Here we addressed the hypothesis that long-term, low-intensity red light exposure at night (rLEN) from a 'safelight' emitting no light below approximately 620 nm disrupts the nocturnal circadian melatonin signal as well as circadian rhythms in circulating metabolites, related regulatory hormones, and physi- ologic parameters. Male Sprague-Dawley rats (n = 12 per group) were maintained on control 12:12-h light:dark (300 lx; lights on, 0600) or experimental 12:12 rLEN (8.1 lx) lighting regimens. After 1 wk, rats underwent 6 low-volume blood draws via cardiocentesis (0400, 0800, 1200, 1600, 2000, and 2400) over a 4-wk period to assess arterial plasma melatonin, total fatty acid, glucose, lactic acid, pO2, pCO2, insulin, leptin and corticosterone concentrations. Results revealed plasma melatonin levels (mean +/- 1 SD) were high in the dark phase (197.5 +/- 4.6 pg/mL) and low in the light phase (2.6 +/- 1.2 pg/mL) of control condi- tions and significantly lower than controls under experimental conditions throughout the 24-h period (P < 0.001). Prominent circadian rhythms of plasma levels of total fatty acid, glucose, lactic acid, pO2, pCO2, insulin, leptin, and corticosterone were significantly (P < 0.05) disrupted under experimental conditions as compared with the corresponding entrained rhythms under control conditions. Therefore, chronic use of low-intensity rLEN from a common safelight disrupts the circadian organization of neuroendocrine, metabolic, and physiologic parameters indicative of animal health and wellbeing.  
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  Notes Approved no  
  Call Number LoNNe @ schroer @ Serial 1583  
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