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Evans, J.A.; Carter, S.N.; Freeman, D.A.; Gorman, M.R. |
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Title |
Dim nighttime illumination alters photoperiodic responses of hamsters through the intergeniculate leaflet and other photic pathways |
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Journal Article |
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Year |
2012 |
Publication |
Neuroscience |
Abbreviated Journal |
Neuroscience |
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Volume |
202 |
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Pages |
300-308 |
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Keywords |
Animals; Biological Clocks/physiology; Circadian Rhythm/physiology; Cricetinae; Darkness; Data Interpretation, Statistical; Geniculate Bodies/*physiology; *Lighting; Male; Motor Activity/physiology; Phodopus; *Photoperiod; Visual Pathways/*physiology |
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Abstract |
In mammals, light entrains the central pacemaker within the suprachiasmatic nucleus (SCN) through both a direct neuronal projection from the retina and an indirect projection from the intergeniculate leaflet (IGL) of the thalamus. Although light comparable in intensity to moonlight is minimally effective at resetting the phase of the circadian clock, dimly lit and completely dark nights are nevertheless perceived differentially by the circadian system, even when nighttime illumination is below putative thresholds for phase resetting. Under a variety of experimental paradigms, dim nighttime illumination exerts effects that may be characterized as enhancing the plasticity of circadian entrainment. For example, relative to completely dark nights, dimly lit nights accelerate development of photoperiodic responses of Siberian hamsters transferred from summer to winter day lengths. Here we assess the neural pathways underlying this response by testing whether IGL lesions eliminate the effects of dim nighttime illumination under short day lengths. Consistent with previous work, dimly lit nights facilitated the expansion of activity duration under short day lengths. Ablation of the IGL, moreover, did not influence photoperiodic responses in animals held under completely dark nights. However, among animals that were provided dimly lit nights, IGL lesions prevented the short-day typical expansion of activity duration as well as the seasonally appropriate gonadal regression and reduction in body weight. Thus, the present data indicate that the IGL plays a central role in mediating the facilitative effects of dim nighttime illumination under short day lengths, but in the absence of the IGL, dim light at night influences photoperiodic responses through residual photic pathways. |
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Department of Psychology, University of California, San Diego, La Jolla, CA, USA. jevans@msm.edu |
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0306-4522 |
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PMID:22155265; PMCID:PMC3578228 |
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IDA @ john @ |
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87 |
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Author |
Topping, M.G.; Millar, J.S.; Goddard, J.A. |
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Title |
The effects of moonlight on nocturnal activity in bushy-tailed wood rats (Neotoma cinerea) |
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Journal Article |
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Year |
1999 |
Publication |
Canadian Journal of Zoology |
Abbreviated Journal |
Can. J. Zool. |
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Volume |
77 |
Issue |
3 |
Pages |
480-485 |
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Keywords |
animals; mammals; rats; bushy-tailed wood rat; Neotoma cinerea; Canada; foraging; reproduction; moonlight; predation risk |
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Abstract |
The nocturnal activity of bushy-tailed wood rats (Neotoma cinerea) was monitored for two breeding seasons (1993 and 1994) in the Canadian Rockies. Radiotelemetry was used under three levels of moonlight to assess two measures of nocturnal activity: (i) the proportion of animals crossing rocky outcrops and entering the surrounding forest to forage, search for mates, or both, and (ii) the distance moved from the den site while in the forest. Males and females exhibited significant differences among moonlight levels, with greater activity on nights of intermediate-level moonlight and less activity on nights with bright or dark moonlight. There was no difference in the proportions of males and females active at any moonlight level. The distances moved from the den did not differ among moonlight levels for either males or females. Having traversed the rocks and entered the forest, individuals moved similar distances regardless of light level. These results suggest that wood rats respond to moonlight only when making the decision to cross rocks and enter the forest. This behaviour presumably serves to counteract the increased risk of predation on bright nights. |
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0008-4301 |
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IDA @ john @ |
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88 |
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Bukalev, A.V.; Vinogradova, I.A.; Zabezhinskii, M.A.; Semenchenko, A.V.; Anisimov, V.N. |
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Title |
Light pollution increases morbidity and mortality rate from different causes in female rats |
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Journal Article |
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Year |
2013 |
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Advances in Gerontology |
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Adv Gerontol |
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3 |
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3 |
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180-188 |
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light-at-night; spontaneous tumors; nontumor pathology epiphysis; rats; animals; mammals |
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The influence of different light regimes (constant light, LL; constant darkness, DD; standard light regime, LD, 12 hours light/12 hours darkness; and natural lighting of the northwest of Russia (NL) on non-tumor pathology revealed in the post-mortem examination of female rats has been studied. It was found that keeping 25-days-old animals under LL and NL conditions led to an increase in the number of infectious diseases and the substantially faster development of spontaneous tumors (2.9 and 3.3 diseases per one rat, respectively), variety of nontumor pathology found in dead rats, compared with the animals in standard (standard light) regime (1.72 diseases per one rat). Light deprivation (DD) led to a substantial reduction in the development of new growth, as well as nontumor and infectious diseases (1.06 diseases per one rat), compared to the same parameters in a standard light regime. |
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2079-0570 |
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IDA @ john @ |
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89 |
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Bedrosian, T.A.; Fonken, L.K.; Walton, J.C.; Nelson, R.J. |
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Title |
Chronic exposure to dim light at night suppresses immune responses in Siberian hamsters |
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Journal Article |
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Year |
2011 |
Publication |
Biology Letters |
Abbreviated Journal |
Biol Lett |
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Volume |
7 |
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3 |
Pages |
468-471 |
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Keywords |
Animals; Blood Bactericidal Activity/immunology; Circadian Rhythm; Cricetinae; Fever/immunology; Hypersensitivity, Delayed/immunology; *Immunity; Light/*adverse effects; Lipopolysaccharides; Locomotion; Phodopus/*immunology |
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Species have been adapted to specific niches optimizing survival and reproduction; however, urbanization by humans has dramatically altered natural habitats. Artificial light at night (LAN), termed 'light pollution', is an often overlooked, yet increasing disruptor of habitats, which perturbs physiological processes that rely on precise light information. For example, LAN alters the timing of reproduction and activity in some species, which decreases the odds of successful breeding and increases the threat of predation for these individuals, leading to reduced fitness. LAN also suppresses immune function, an important proxy for survival. To investigate the impact of LAN in a species naive to light pollution in its native habitat, immune function was examined in Siberian hamsters derived from wild-caught stock. After four weeks exposure to dim LAN, immune responses to three different challenges were assessed: (i) delayed-type hypersensitivity (DTH), (ii) lipopolysaccharide-induced fever, and (iii) bactericide activity of blood. LAN suppressed DTH response and reduced bactericide activity of blood after lipopolysaccharide treatment, in addition to altering daily patterns of locomotor activity, suggesting that human encroachment on habitats via night-time lighting may inadvertently compromise immune function and ultimately fitness. |
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Department of Neuroscience, The Ohio State University Medical Center, Columbus, OH 43210, USA. tracy.bedrosian@osumc.edu |
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1744-9561 |
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PMID:21270021; PMCID:PMC3097873 |
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IDA @ john @ |
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90 |
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Fonken, L.K.; Kitsmiller, E.; Smale, L.; Nelson, R.J. |
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Title |
Dim nighttime light impairs cognition and provokes depressive-like responses in a diurnal rodent |
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Journal Article |
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Year |
2012 |
Publication |
Journal of Biological Rhythms |
Abbreviated Journal |
J Biol Rhythms |
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27 |
Issue |
4 |
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319-327 |
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Analysis of Variance; Animals; CA1 Region, Hippocampal/cytology; CA3 Region, Hippocampal/cytology; Circadian Rhythm/*physiology; Cognition/*physiology/radiation effects; Corticosterone/blood; Dendrites/physiology/radiation effects; Dentate Gyrus/cytology; Depressive Disorder/*physiopathology; Food Preferences/physiology/radiation effects; Light; Male; Maze Learning/physiology/radiation effects; Motor Activity/physiology/radiation effects; Murinae/*physiology; Neurons/drug effects/physiology; *Photoperiod; Swimming/physiology |
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Circadian disruption is a common by-product of modern life. Although jet lag and shift work are well-documented challenges to circadian organization, many more subtle environmental changes cause circadian disruption. For example, frequent fluctuations in the timing of the sleep/wake schedule, as well as exposure to nighttime lighting, likely affect the circadian system. Most studies of these effects have focused on nocturnal rodents, which are very different from diurnal species with respect to their patterns of light exposure and the effects that light can have on their activity. Thus, the authors investigated the effect of nighttime light on behavior and the brain of a diurnal rodent, the Nile grass rat. Following 3 weeks of exposure to standard light/dark (LD; 14:10 light [~150 lux] /dark [0 lux]) or dim light at night (dLAN; 14:10 light [~150 lux] /dim [5 lux]), rats underwent behavioral testing, and hippocampal neurons within CA1, CA3, and the dentate gyrus (DG) were examined. Three behavioral effects of dLAN were observed: (1) decreased preference for a sucrose solution, (2) increased latency to float in a forced swim test, and (3) impaired learning and memory in the Barnes maze. Light at night also reduced dendritic length in DG and basilar CA1 dendrites. Dendritic length in the DG positively correlated with sucrose consumption in the sucrose anhedonia task. Nighttime light exposure did not disrupt the pattern of circadian locomotor activity, and all grass rats maintained a diurnal activity pattern. Together, these data suggest that exposure to dLAN can alter affective responses and impair cognition in a diurnal animal. |
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Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA. fonken.1@osu.edu |
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0748-7304 |
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PMID:22855576 |
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IDA @ john @ |
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91 |
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