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  • 1
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Reproduction of many temperate zone birds is under photoperiodic control. The Japanese quail is an excellent model for studying the mechanism of photoperiodic time measurement because of its distinct and marked response to changing photoperiods. Studies on this animal have suggested that the ...
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 141 (1981), S. 207-214 
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The roles of the pineal organ and the suprachiasmatic nucleus (SCN) in the control of circadian rhythms of locomotor activity were examined in male Java sparrows (Padda oryzivora). 1. Removal of the pineal organ resulted in (i) no interference with entrainment to a light-dark (LD) cycle with anticipatory activity, (ii) appearance of residual circadian rhythmicity for a while after transfer from an LD cycle to a continuous dim light condition (LL), and (iii) subsequent loss of the circadian locomotor rhythms in prolonged LL (Fig. 1). 2. Birds with bilateral SCN lesions showed diurnal rhythms with anticipatory activity in LD cycles, but did not show any circadian rhythms in LL (Fig. 2). Unilateral lesions of the SCN did not lead to loss of circadian rhythms in LL. The length of the circadian period (τ), however, changed for about a month. 3. Continuous administration of melatonin induced suppression of the circadian activity rhythms and reduced total amount of locomotor activity in LL (Fig. 3). These results suggest that in the Java sparrow the circadian rhythms of locomotor activity are regulated by a pineal-suprachiasmatic complex.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1432-1351
    Schlagwort(e): Circadian rhythm ; Locomotor activity ; Body temperature ; Melatonin ; Pigeon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Although pinealectomy or blinding resulted in loss of the clarity of the free-running rhythm of locomotor activity and body temperature and reduced the peak level of circulating melatonin rhythms to approximately a half in intact pigeons, neither pinealectomy nor blinding abolished any of these rhythms. However, when pinealectomy and blinding were combined, the rhythms of locomotor activity and body temperature disappeared in prolonged constant dim light, and melatonin concentration was reduced to the minimum level of detection. In order to examine the role of melatonin in the pigeon's circadian system, it was administered either daily or continuously to PX + EX-pigeons in LLdim. Daily administration of melatonin restored circadian rhythms of locomotor activity which entrained to melatonin injections, but continuous administration did not induce any remarkable change of locomotor activity. These results suggest that melatonin synthesized in the pineal body and the eye contributes to circulating melatonin and its rhythmicity is important for the control of circadian rhythms of locomotor activity and body temperature in the pigeon.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Locomotor activity and feeding activity were measured together with circulating levels of melatonin in pigeons which were exposed to constant bright light (LLbright, 2000 lux) following light-dark (LD) cycles. Although all the pigeons showed daily rhythms of locomotor activity, feeding activity, and melatonin levels under LD cycles, they lost all the rhythms in prolonged LLbright. Acute exposure to bright light (2000 lux) during darkness reduced plasma melatonin levels. The half-time for the suppression in melatonin levels was about 30 min after short-term light exposure. These results support the hypothesis that melatonin may control the circadian rhythms of locomotor activity and feeding activity in the pigeon.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 154 (1984), S. 59-69 
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The roles of the pineal organ and the eye in the control of circadian locomotor rhythmicity were studied in the pigeon (Columba livia). Neither pinealectomy nor blinding abolished the circadian rhythms in constant dim light conditions (LLdim). All the pinealectomized birds and the blinded birds entrained to light-dark (LD) cycles with no discernible anticipatory activity. However, the birds which had been both pinealectomized and blinded showed no circadian rhythms in prolonged LLdim. These birds entrained to LD cycles with anticipatory activity and showed residual rhythmicity for a while after transfer from LD cycles to LLdim. Continuous administration of melatonin induced suppression of the circadian rhythms and reduced total amount of locomotor activity in LLdim. These results suggest that not only the pineal organ but also the eye (perhaps the retina) is involved in the pigeon's circadian system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 171 (1992), S. 63-67 
    ISSN: 1432-1351
    Schlagwort(e): Circadian rhythms ; Feeding ; Locomotor activity ; Starlings ; Internal desynchronization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary In higher organisms, many physiological and behavioral functions exhibit daily variations, generated by endogenous circadian oscillators. It is not yet clear whether all the various rhythms that occur within an individual depend on one and the same pacemaker or whether different pacemakers are involved. To examine this question, the feeding and perch-hopping rhythms were measured in European starlings (Sturnus vulgaris) under light-dark cycles and continuous dim light. In dim light, the internal phase relationship between the feeding and perch-hopping rhythms changed systematically as a function of the circadian period, and the two rhythms could even dissociate and show different circadian periods in individuals with extremely long or extremely short circadian periods. Moreover, in some birds kept on lowamplitude light-dark cycles, the rhythm of feeding was synchronized 180° out of phase with the rhythm of locomotor activity. These results strongly suggest that in the European starling the feeding and locomotor activity rhythms are controlled by separate circadian pacemakers.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1432-0878
    Schlagwort(e): Key words: Pineal organ ; Pinealocytes ; Pineal photoreceptors ; Sensory structures ; Photopigment ; Pinopsin ; Immunocytochemistry ; Chicken
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Pinopsin is a photoreceptive molecule cloned from the chicken pineal organ. An antibody highly specific for pinopsin was applied in light- and electron-microscopic immunocytochemical studies of the pineal organ of 1 to 2-month-old chickens. Intense immunoreactivity was found in the follicular lumen at the light-microscopic level. In addition, small immunoreactive spherical or fibrous structures were diffusely distributed at the parafollicular aspect of the pineal organ. To identify immunoreactive elements precisely, we used pre-embedding immunoelectron microscopy. These studies revealed immunoreactive outer segments of pinealocytes arranged closely side by side in the follicular lumina. The thin initial portion of the outer segment arose from a basal body located in the inner segment. Immunoreactive pear-shaped outer segments occupied small lumina. Follicular lumina displayed immunonegative arrays of whorl-like lamellar membranes. Occasionally, these immunonegative structures were surrounded by immunoreactive concentric lamellar complexes. In the parafollicular pineal parenchyma, long slender cilium-like structures or enlarged cilia and concentric lamellar arrays showed intense immunoreactivity. All immunoreactive structures observed in this study were considered to represent outer segments of pinealocytes of the chicken pineal organ.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1432-0878
    Schlagwort(e): Key words: Cerebrospinal fluid-contacting neurons ; Vasoactive intestinal peptide (VIP) ; Immuno-electron microscopy ; Lateral septum ; Pigeon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Vasoactive intestinal peptide (VIP)-like immunoreactive terminal fields were examined in the lateral septum of the pigeon by means of immunocytochemistry. According to light-microscopic observations, these projections originated from VIP-like immunoreactive cerebrospinal fluid (CSF)-contacting neurons, which are located in the ependymal layer of the lateral septum and form a part of the lateral septal organ. The processes of these cells gave rise to dense terminal-like structures in the lateral septum. Pre-embedding immuno-electron microscopy revealed that VIP-like immunoreactive axon terminals had synaptoid contacts with perikarya of small VIP-immunonegative neurons of the lateral septum, which were characterized by an invaginated nucleus, numerous mitochondria, a well-developed Golgi apparatus, endoplasmic reticulum and a small number of dense-core vesicles (about 100 nm in diameter). VIP-like immunoreactive axons were also seen in contact with immunonegative dendrites in the lateral septum. In both axosomatic and axodendritic connections, VIP-like immunoreactive presynaptic terminals contained large dense-core vesicles, clusters of small vesicles and mitochondria. These findings suggest that VIP-immunoreactive neurons of the lateral septal organ project to small, presumably peptidergic nerve cells of the lateral septum and that the VIP-like neuropeptide serves as a neuromodulator (-transmitter) in this area.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 1432-0878
    Schlagwort(e): Cerebrospinal fluid-contacting neurons ; Vasoactive intestinal peptide (VIP) ; Immuno-electron microscopy ; Lateral septum ; Pigeon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Vasoactive intestinal peptide (VIP)-like immunoreactive terminal fields were examined in the lateral septum of the pigeon by means of immunocytochemistry. According to light-microscopic observations, these projections originated from VIP-like immunoreactive cerebrospinal fluid (CSF)-contacting neurons, which are located in the ependymal layer of the lateral septum and form a part of the lateral septal organ. The processes of these cells gave rise to dense terminal-like structures in the lateral septum. Pre-embedding immuno-electron microscopy revealed that VIP-like immunoreactive axon terminals had synaptoid contacts with perikarya of small VIP-immunonegative neurons of the lateral septum, which were characterized by an invaginated nucleus, numerous mitochondria, a well-developed Golgi apparatus, endoplasmic reticulum and a small number of dense-core vesicles (about 100 nm in diameter). VIP-like immunoreactive axons were also seen in contact with immunonegative dendrites in the lateral septum. In both axosomatic and axodendritic connections, VIP-like immunoreactive presynaptic terminals contained large dense-core vesicles, clusters of small vesicles and mitochondria. These findings suggest that VIP-immunoreactive neurons of the lateral septal organ project to small, presumably peptidergic nerve cells of the lateral septum and that the VIP-like neuropeptide serves as a neuromodulator (-transmitter) in this area.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    ISSN: 1573-3297
    Schlagwort(e): SM/J mice ; A/J mice ; SMXA recombinant inbred strains ; quantitative trait locus ; circadian rhythm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract SM/J and A/J inbred strain of mice have different characteristics in circadian behaviors such as free-running period (τ), phase relationship (ψ) between light-dark cycles and activity rhythms, and amount of wheel-running activity. To determine the genes which affect these behaviors, a quantitative trait locus (QTL) analysis using SMXA recombinant inbred strains derived from SM/J and A/J mice was performed. Concerning τ, two regions on chromosomes (Chrs) 7 and 18 surpassed the genome-wide suggestive level. As for ψ, one suggestive QTL was detected on Chr 7. The QTLs which affect daily activity counts under light-dark cycles and constant darkness were mapped to the same chromosomal regions on Chrs 1 and 17, respectively. The provisional QTLs detected in the present study might be useful for understanding the complex mechanism regulating circadian behaviors.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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