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  • Melatonin  (7)
  • Ultrastructure  (5)
  • pineal  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Vasopressin and oxytocin modulation of melatonin secretion from rat pineal glands
    Amsterdam : Elsevier
    Peptides 11 (1990), S. 1075-1079 
    Details
    ISSN: 0196-9781
    Keywords: Melatonin ; Oxytocin ; Perifusion ; Pineal gland ; Vasopressin
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0196-9781(90)90133-P
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  • 2
    Electronic Resource
    Electronic Resource
    Circadian rhythmicity of the activity of hydroxyindole-o-methyl transferase (HIOMT) in the formation of melatonin and 5-methoxytryptophol in the pineal, retina, and harderian gland of the golden hamster (1980)
    Springer
    Journal of neural transmission 49 (1980), S. 229-245 
    Details
    ISSN: 1435-1463
    Keywords: Melatonin ; 5-methoxytryptophol ; HIOMT ; pineal ; retina ; Harderian gland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The day and night rhythms in the activity of HIOMT in the formation of melatonin and of 5-methoxytryptophol have been determined in the pineal, retina and Harderian gland of the adult male golden hamster. In all hamsters used there was no detectable HIOMT activity in the deep pineal. In the superficial pineal HIOMT activity, involved in the synthesis of melatonin (Mel), was observed to be high at the end of the dark period and at the middle of the light period. Considering the HIOMT activity involved in the production of 5-methoxytryptophol (5-MTL), an increase in 5-MTL synthesis was observed only during the light period. Comparing the peak of Mel-production with that of 5-MTL it appears that during the light period the pineal produces more 5-MTL than Mel. In the Harderian glands, the circadian course of HIOMT activity involved in the synthesis of Mel seems to run parallel to that of the enzyme implicated in 5-MTL synthesis, both being stimulated at the end of the dark period. The activity of HIOMT in 5-MTL production is, however, always approximately 2 times higher than for Mel synthesis. In the retina the synthesis of Mel and 5-MTL is not significantly higher during the dark period than during the light period. However, the production of 5-MTL is larger than that of Mel. It appears that (1) with the exception of the end of the dark period, the extra-pineal synthesis of Mel and 5-MTL is always higher than that in the pineal; (2) the circadian synthesis of 5-methoxyindoles is different in each organ, and (3) in the pineal the circadian activity of HIOMT involved in 5-MTL formation is different from that of the same enzyme involved in the formation of Mel. The results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01252128
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of 5-methoxytryptamine on testicular atrophy induced by experimental or natural short photoperiods in the golden hamster (mesocricetus auratus) (1982)
    Springer
    Journal of neural transmission 55 (1982), S. 69-84 
    Details
    ISSN: 1435-1463
    Keywords: 5-methoxytryptamine ; pineal ; hamster ; reproductive function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Subcutaneous implantation of 5-methoxytryptamine-filled silastic capsules overcomes, in natural as well as in experimental conditions, the inhibitory effect of short photoperiod on the gonadal axis. The results obtained are similar to those obtained after pinealectomy. They indicate that 5-methoxytryptamine when constantly available presents, like melatonin, a progonadal (or counter-antigonadal) effect. Evidently, 5-methoxytryptamine, like melatonin, is involved in the control of the reproductive function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243342
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  • 4
    Electronic Resource
    Electronic Resource
    Morning injections of large doses of melatonin, but not of 5-methoxytryptamine, prevent in the hamster the antigonadotropic effect of 5-methoxytryptamine administered late in the afternoon (1982)
    Springer
    Journal of neural transmission 55 (1982), S. 85-93 
    Details
    ISSN: 1435-1463
    Keywords: melatonine ; 5-methoxytryptamine ; pineal ; hamster ; photo-period
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Late-afternoon-administered 5-methoxytryptamine (5-MT) induces gonadal atrophy in male hamsters kept under long photoperiods (14 hL/ 10 hD). Morning-injection of 1mg 5-MT does not show antigonadal effects. However, 1 mg melatonin (MEL) administered in the morning completely prevents the antigonadotropic effect of 5-MT administered in the late afternoon. This result is specific of MEL since morning injections of 1mg 5-MT do not present this counterantigonadotropic property. When interpreted according to Reiter's concept of down-regulation of MEL receptors, these results suggest that the physiological effects of 5-MT are indirectly due to MEL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243343
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  • 5
    Electronic Resource
    Electronic Resource
    Daily 5-methoxytryptamine injections inhibit short-day-induced testicular atrophy in golden hamsters (1982)
    Springer
    Journal of neural transmission 55 (1982), S. 95-99 
    Details
    ISSN: 1435-1463
    Keywords: 5-methoxytryptamine ; hamster ; pineal ; photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Daily (6 days on 7) subcutaneous injections of 25μg of 5-methoxytryptamine in saline 0.9% into intact male hamsters given between 9.00 and 9.30 (lights on from 8.00 to 18.00; 10hL/14 hD) during 8 weeks block short photoperiodically induced testicular atrophy. Under these experimental conditions, however, this blockage is not total since the weight of the testes and of the accessory sex organs of the pinealectomized hamsters is higher than that of treated animals. The results indicate that 5-MT, like melatonin, is a physiologically active compound implicated in the control of the reproductive function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243344
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  • 6
    Electronic Resource
    Electronic Resource
    Melatonin: presence and formation in invertebrates (1993)
    Springer
    Cellular and molecular life sciences 49 (1993), S. 642-647 
    Details
    ISSN: 1420-9071
    Keywords: Melatonin ; day-night rhythm ; N-acetylserotonin (NAS) ; N-acetyltransferase (NAT) ; invertebrates ; photoreceptors ; circadian pacemakers ; photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In vertebrates, it is now clearly demonstrated that the pineal gland is implicated in conveying photoperiodic information via the daily pattern of melatonin secretion. Invertebrates, like vertebrates, use photoperiodic changes as a temporal cue to initiate physiological processes such as reproduction or diapause. How this information is integrated in invertebrates remains an unsolved question. Our review will be an attempt to evaluate the possible role of melatonin in conveying photoperiodic information in invertebrates. It is now well demonstrated in both vertebrates and invertebrates that melatonin as well as its precursors or synthesizing enzymes are present in various organs implicated in photoreceptive processes or in circadian pacemaking. Melatonin, serotonin or N-acetyltransferase have been found in the head, the eyes, the optic lobe and the brain of various invertebrate species. In some species it has also been shown that melatonin is produced rhythmically with high concentrations reached during the dark period. Moreover, the physiological effects of melatonin on various periodic processes such as rhythmic contractions in coelenterates, fissioning of asexual planarians or reproductive events in flies have been reported in the literature. All these results support the hypothesis (refs 36, 37) that melatonin is not solely a pineal hormone but that it may be an evolutionary conservative molecule principally involved in the transduction of photoperiodic information in all living organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01923945
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  • 7
    Electronic Resource
    Electronic Resource
    The pineal gland of nocturnal mammals (1981)
    Springer
    Cell & tissue research 216 (1981), S. 253-271 
    Details
    ISSN: 1432-0878
    Keywords: Pinealocytes ; Cell populations ; Bat ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the pineal gland of the pipistrelle bat two different populations of pinealocytes and glial cells were observed electron microscopically. The pinealocytes of populations I and II differ in their content of metabolically active cell organelles. In the pinealocytes of population I, granular vesicles originating from the Golgi apparatus were found in the perikaryon and especially in the endings of the pinealocyte processes. Granular vesicles appeared to be more numerous in hibernating nulliparous females. The pinealocytes of population II are characterized by the presence of small cytoplasmic vacuoles, probably originating from cisternae of the granular endoplasmic reticulum and containing flocculent material of moderate electron density. The classification of the pinealocytes belonging to population II is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233619
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of a short light pulse at night on the ultrastructure of the rat pinealocyte: a quantitative study (1988)
    Springer
    Cell & tissue research 254 (1988), S. 247-249 
    Details
    ISSN: 1432-0878
    Keywords: Pinealocyte ; Light exposure ; Ultrastructure ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Although it is generally known that light strongly influences N-acetyltransferase activity and melatonin production in the pineal gland, little information is available concerning morphological changes following light exposure. As exposure of rats to a short light pulse at night rapidly depresses melatonin synthesis, we decided to determine whether this experimental condition produces rapid changes in the pinealocyte organelles. A 30-min light pulse at night (six hours after lights out) provoked rapid changes in the relative volumes of some pinealocyte organelles. The volume fractions of mitochondria, Golgi apparatus and lipid droplets, and the numbers of dense-core vesicles and “synaptic” ribbons decreased, whereas the volume fraction of lysosomes increased. There were no differences in the volumes of granular endoplasmic reticulum and vacuoles containing flocculent material in those animals exposed to light compared with control animals. These results indicate that a short light pulse at night causes ultrastructural changes that can be interpreted as morphological features of diminished activity of pinealocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220041
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  • 9
    Electronic Resource
    Electronic Resource
    An attempt to correlate brain areas containing melatonin-binding sites with rhythmic functions: a study in five hibernator species (1994)
    Springer
    Cell & tissue research 278 (1994), S. 97-106 
    Details
    ISSN: 1432-0878
    Keywords: Melatonin receptors ; Pituitary gland, pars tuberalis ; Hibernators ; Autoradiography ; Melatonin ; 2-Iodomelatonin ; Jaculus orientalis, Eliomys quercinus, Glis glis, Cricetus cricetus (Rodentia), Erinaceus europaeus (Insectivora)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract High affinity melatonin-binding sites have been described, by means of autoradiography with 2-125I-melatonin as the ligand, in more than 60 brain areas of about 20 mammalian species, with dramatic variations in the nature and number of labelled structures among the different species studied. As melatonin is involved in the synchronization of biological rhythms, we have tried to correlate the brain areas containing melatonin-binding sites with some rhythmic functions typical of give species. Therefore, we have studied the location of melatonin-binding sites in the complete brain of five long-day breeders with hibernation cycles, viz. one insectivore and four rodents. With the exception of the suprachiasmatic nuclei and the pars tuberalis of the pituitary, both of which contain binding sites in all five species, few reactive structures are common, even among species from the same family, e.g. the edible dormouse and the garden dormouse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305781
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  • 10
    Electronic Resource
    Electronic Resource
    The pineal gland of equatorial mammals (1980)
    Springer
    Cell & tissue research 210 (1980), S. 417-433 
    Details
    ISSN: 1432-0878
    Keywords: Pinealocytes ; Ultrastructure ; Malaysian rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Résumé Les pinéalocytes d'un Rat de Malaisie (Rattus sabanus), un animal vivant près de l'équateur donc dans une zone où les variations annuelles de la longueur des jours sont minimes, examinés au microscope électronique ont été comparés à ceux d'autres Mammifères. Une seule population de pinéalocytes a été observée. La présence d'un grand nombre de vésicules granulaires et de rubans circonscrits par des vésicules est la caractéristique premi`ere des pinéalocytes de cette espèce. Les rubans circonscrits par des vésicules ont été plus spécialement observés dans les terminaisons des prolongements des pinéalocytes où ils sont nombreux et la plus souvent en contact directe avec l'espace périvasculaire. L'importance physiologique de ces rubans circonscrits par des vésicules et des vésicules granulaires est discuté.
    Notes: Summary The ultrastructure of the pinealocytes of the Malaysian rat (Rattus sabanus), a mammal inhabiting a zone near the equator where the annual variations of daylength are inconspicuous, was examined and compared with that of pinealocytes of other mammals. On the basis of the presence of granular vesicles, only one population of pinealocytes was found. A large number of granular vesicles and vesicle-crowned rodlets is characteristic of the pinealocytes of this equatorial species. Vesicle-crowned rodlets are especially numerous in the endings of the pinealocyte processes and; they most often found in direct topographical connection with the perivascular spaces. The physiological significance of the presence of such large amounts of vesicle-crowned rodlets and of the secretory process characterized by the formation of granular vesicles is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220199
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