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  • 1
    Electronic Resource
    Electronic Resource
    Spectral sensitivity of a novel photoreceptive system mediating entrainment of mammalian circadian rhythms (1984)
    [s.l.] : Nature Publishing Group
    Nature 308 (1984), S. 186-188 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] While all other vertebrates have extraretinal photoreceptive input to the circadian system5, in mammals the photoreceptors for entrainment and phase shifting are located in the eye6,7 A specialized retinal projection terminating in the suprachiasmatic nuclei of the hypothalamus conveys photic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/308186a0
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  • 2
    Electronic Resource
    Electronic Resource
    Extraretinal light perception in the sparrow IV. Further evidence that the eyes do not participate in photoperiodic photoreception (1975)
    Springer
    Journal of comparative physiology 97 (1975), S. 205-213 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Photoperiodic testicular growth in House Sparrows (Passer domesticus) exposed to long days (16 hrs) of orange-red light ({ie205-01}600 nm) is exclusively controlled by extraretinal photoreceptors in the brain; the eyes are not involved. Careful reconsideration of previously published data from this and other bird species does not support a role for the eyes in photoperiodically significant photoreception.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617543
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  • 3
    Electronic Resource
    Electronic Resource
    Pineal and locomotor activity (1972)
    Springer
    Journal of comparative physiology 77 (1972), S. 163-169 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Perch-hopping activity patterns of pinealectomized and normal house sparrows,Passer domesticus, were examined by power spectral analysis and by analysis of daily totals. Power spectral analysis strengthened our previous conclusion that circadian periodicity is absent from the activity of pinealectomized birds kept in constant conditions. The spectral analyses also revealed that obvious ultradian rhythms are not present in sparrow perching activity. Pinealectomy had no effect on the daily activity totals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693604
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  • 4
    Electronic Resource
    Electronic Resource
    Multiple redundant circadian oscillators within the isolated avian pineal gland (1984)
    Springer
    Journal of comparative physiology 154 (1984), S. 435-440 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The avian pineal gland contains a circadian pacemaker that oscillates in vitro. Using a flow-through culture system it is possible to measure melatonin production from very small subsections of an individual gland. We have used this technique to attempt to localize the oscillators in the pineal. Progressive tissue reduction did not affect the rhythmicity of cultured pineals. Multiple pieces (up to eight) from a single pineal all were capable of circadian oscillation — establishing directly that a pineal gland contains at least eight oscillators. All pineal pieces were responsive to light, and single light pulses shifted the phase of the melatonin rhythm. Because pieces equivalent to less than one per cent of the whole gland were rhythmic and because the capacity for oscillation was distributed throughout the gland, an individual pineal appears to be composed of a population of circadian oscillators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00605243
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  • 5
    Electronic Resource
    Electronic Resource
    Contribution of pineal and retinae to the circadian rhythms of circulating melatonin in pigeons (1988)
    Springer
    Journal of comparative physiology 164 (1988), S. 25-30 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Melatonin levels in the plasma of homing pigeons were measured by radioimmunoassay. In a 12∶12 LD cycle a robust daily rhythm of plasma melatonin was found in intact birds. This rhythm is significantly reduced in amplitude after pinealectomy, and disappears completely after the pinealectomized animals have been bilaterally enucleated. The results indicate that in the pigeon 70% of the nighttime peak of blood-borne melatonin comes from the pineal gland, while 17% comes from the retina. In addition, there is a relatively large amount (13%) of non-rhythmic melatonin of unidentified origin. The melatonin rhythm appears to be circadian in nature, since melatonin levels begin to fall before lights-on in LD, and rhythmicity persists in intact and pinealectomized birds for at least two cycles in DD. In conjunction with earlier studies, the present results are consistent with the hypothesis that melatonin serves as mediator of circadian information in the pigeon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00612714
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  • 6
    Electronic Resource
    Electronic Resource
    Circadian locomotor rhythms in the desert iguana I. The role of the eyes and the pineal (1990)
    Springer
    Journal of comparative physiology 166 (1990), S. 803-810 
    Details
    ISSN: 1432-1351
    Keywords: Circadian ; Lizard ; Pineal ; Eye ; Melatonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pineal and the eyes are known to be important components in the circadian system of some species of lizards; their effects may be mediated by the hormone melatonin. We examined the role played by these structures in the desert iguana (Dipsosaurus dorsalis). Surgical removal of the pineal had no effect on circadian locomotor rhythms, even though this procedure abolished the circadian rhythm of melatonin in the blood. Furthermore, when the isolated pineal of Dipsosaurus was studied in organ culture, it showed no circadian rhythm of melatonin secretion, as do pineals of some other lizard species, although it did produce large quantities of this hormone. Bilateral ocular enucleation had only small effects on the freerunning period of locomotor rhythms, without affecting melatonin levels in the blood. Behavioral circadian rhythms persisted in desert iguanas subjected to both enucleation and pinealectomy. These data suggest that neither the pineal nor the eyes are central components of the circadian pacemaking system in Dipsosaurus, nor is melatonin critically involved in maintaining its organization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187326
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  • 7
    Electronic Resource
    Electronic Resource
    Circadian locomotor rhythms in the desert iguana (1990)
    Springer
    Journal of comparative physiology 166 (1990), S. 811-816 
    Details
    ISSN: 1432-1351
    Keywords: Circadian ; Lizard ; Suprachiasmatic nucleus ; Hypothalamus ; Lesion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Desert iguanas, Dipsosaurus dorsalis, displaying freerunning circadian locomotor rhythms in conditions of constant darkness and temperature received electrolytic lesions to the hypothalamus. The locomotor activity of those lizards (N = 9) which sustained 80% or more damage to the suprachiasmatic nucleus (SCN) became arrhythmic whereas all animals that sustained less than 35% damage to the SCN remained rhythmic, even though they sustained significant damage to nearby regions of the hypothalamus and preoptic area. These results suggest strongly that the SCN plays a role in the regulation of circadian rhythms in the desert iguana. Taken together with other evidence, they support the view that this structure is homologous to the mammalian SCN, which acts as a pacemaker in the circadian system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187327
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  • 8
    Electronic Resource
    Electronic Resource
    Social stimuli fail to act as entraining agents of circadian rhythms in the golden hamster (1992)
    Springer
    Journal of comparative physiology 170 (1992), S. 181-187 
    Details
    ISSN: 1432-1351
    Keywords: Circadian rhythm ; Entrainment ; Social interaction ; Locomotor activity ; Body temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ability of social stimuli to act as entraining agents of circadian rhythms was investigated in golden hamsters (Mesocricetus auratus). In a first experiment, pairs of male hamsters (one of them enucleated and the other intact) were maintained under a light-dark (LD) cycle with a period of 23.3 h. Running-wheel activity was recorded to determine the effect of social interaction on the free-running circadian rhythm of activity. In several pairs, general activity and body temperature were also recorded. In all pairs the intact animals entrained to the LD cycle, whereas the activity rhythms of the enucleated animals free-ran with periods of approximately 24 h and showed no apparent sign of synchronization or relative coordination with the other member of the pair. In a second experiment, male hamsters maintained in constant darkness received pulses of social interaction, which have been reported to induce phase shifts of the activity rhythm. Consistent phase shifts in the running-wheel activity rhythm were not induced by the social pulses in our experiment. These results suggest strongly that social stimuli are not effective entraining agents of circadian rhythms in the golden hamster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196900
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of physiological cycles of infused melatonin on circadian rhythmicity in pigeons (1992)
    Springer
    Journal of comparative physiology 170 (1992), S. 615-622 
    Details
    ISSN: 1432-1351
    Keywords: Melatonin ; Circadian rhythms ; Infusions ; Behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The role of the hormone melatonin in the circadian system of pigeons (Columba livia) was investigated. Using an automatic infusion system, melatoni at physiological levels was delivered for 10 h each day to cannulated, pinealectomized (P-X) pigeons in constant darkness. These cyclic infusions of melatonin entrained feeding rhythms in P-X pigeons while vehicle infusions were ineffective entraining agents. When the retinae of P-X pigeons were removed (E-X), feeding rhythms were abolished in constant darkness. When cyclic melatonin infusions were delivered to these birds (E-X and P-X), feeding rhythmicity was restored whereas vehicle infusions alone did not restore rhythmicity. When melatonin infusions were terminated in E-X/P-X pigeons, feeding rhythms persisted for several days but eventually decayed. Blood melatonin levels were measured in both P-X and E-X/P-X birds infused cyclically with exogenous melatonin and were found to be within the physiological range both in level and pattern. These results strongly suggest that endogenous melatonin, released by the pineal gland and the retinae, regulates the timing of feeding rhythms by entraining other oscillators in the circadian system of the pigeon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199337
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  • 10
    Electronic Resource
    Electronic Resource
    Development of the mouse circadian pacemaker: Independence from environmental cycles (1981)
    Springer
    Journal of comparative physiology 143 (1981), S. 527-539 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The freerunning period (τ) of the circadian pacemaker underlying the wheel-running activity rhythm ofMus musculus was found to be unaffected by the periods of environmental cycles (maternal and light/dark) under which the mice are raised. Mice born to mothers entrained to periods (T) of 28 or 20 h (ratio of light to dark of 14/10) and maintained on those cycle until beyond puberty showed only a temporary difference in freerunning period when placed into constant darkness. Such temporary ‘after-effects’ of entrainment were shown, as had been previously, to occur in animals exposed to non-24-h cycles as adults only. 2. After-effects on the ratio of activity to rest (α/ϱ) were not even temporarily different in animals raised onT=28 or T=20. 3. Rearing on T=28 or T=20 did not affect the abilities of animals to entrain to these cycles later in life. 4. Measurements from young and old animals as well as remeasurement of the young animals later in their lives revealed several effects of age on the pacemaker: a) After-effects on freerunning period after T = 28 or T = 20 are not greater but last longer in older animals; b) Freerunning period is shorter in younger animals; and c) The ratio of activity to rest changes over time in constant darkness and is greater in young animals. Together these suggest that pacemaker ‘plasticity’ reflected in changes in τ and α/ϱ over time in constant darkness decreases with age. 5. The length of gestation measured in ‘real’ time was the same in mice entrained to T = 28 or T=20, demonstrating that gestation is not measured in circadian cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00609919
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