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Author Shuboni, D; Yan, L url  doi
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  Title (up) Nighttime dim light exposure alters the responses of the circadian system Type Journal Article
  Year 2010 Publication Neuroscience Abbreviated Journal  
  Volume 170 Issue 4 Pages 1172-1178  
  Keywords animals; rodents; animal behaviour: human physiology  
  Abstract The daily light dark cycle is the most salient entraining factor for the circadian system. However, in modern society, darkness at night is vanishing as light pollution steadily increases. The impact of brighter nights on wild life ecology and human physiology is just now being recognized. In the present study, we tested the possible detrimental effects of dim light exposure on the regulation of circadian rhythms, using CD1 mice housed in light/dim light (LdimL, 300 lux:20 lux) or light/dark (LD, 300 lux:1 lux) conditions. We first examined the expression of clock genes in the suprachiasmatic nucleus (SCN), the locus of the principal brain clock, in the animals of the LD and LdimL groups. Under the entrained condition, there was no difference in PER1 peak expression between the two groups, but at the trough of the PER 1 rhythm, there was an increase in PER1 in the LdimL group, indicating a decrease in the amplitude of the PER1 rhythm. After a brief light exposure (30 min, 300 lux) at night, the light-induced expression of mPer1 and mPer2 genes was attenuated in the SCN of LdimL group. Next, we examined the behavioral rhythms by monitoring wheel-running activity to determine whether the altered responses in the SCN of LdimL group have behavioral consequence. Compared to the LD controls, the LdimL group showed increased daytime activity. After being released into constant darkness, the LdimL group displayed shorter free-running periods. Furthermore, following the light exposure, the phase shifting responses were smaller in the LdimL group. The results indicate that nighttime dim light exposure can cause functional changes of the circadian system, and suggest that altered circadian function could be one of the mechanisms underlying the adverse effects of light pollution on wild life ecology and human physiology.  
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  Call Number LoNNe @ schroer @ Serial 1601  
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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 (up) 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 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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