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  • 1
    ISSN: 0300-9629
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0531-5565
    Keywords: aging ; pineal gland ; rat ; sympathetic innervation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Pineal gland ; Organ culture ; Synaptic ribbons ; Synaptic spherules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study pineal glands of rats aged 69–71 days were studied in vivo and in vitro with respect to day/night changes of “synaptic” ribbons and spherules. It was found that ribbons outnumber spherules by a factor of 3. In vivo, both ribbons and spherules show a roughly 3-fold increase in number at 1 a.m. when compared to 1 p.m. Up to 39 h in vitro, the two structures in question did not reveal day/night differences in amount, suggesting that diurnal rhythmicity of the gland did apparently not persist in organ culture. After 3 h in organ culture, the spherules, but not the ribbons, showed a striking increase in number, showing that ribbons and spherules may be governed by different mechanisms.
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  • 4
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The aim of the present investigation was to study the distribution in the rat pineal gland of dopamine-β-hydroxylase (DBH) which is essential for the formation of the melatonin synthesis-regulating substance noradrenaline (NA). In 5- and 8-month-old male Sprague-Dawley rats DBH-like immunoreactivity (DBH-LI) was studied using polyclonal antibodies against DBH and the indirect immunofluorescent technique. DBH-LI was mainly located in pincal nerve fibres coming from the superior cervical ganglia. The intensity of the staining reaction was considerably lower than in non-pineal noradrenergic nerve fibres and the impression was gained by comparison of DBH-LI specimens with glyoxylic acid-treated sections that only approximately one third of the NA-containing intrapineal nerve fibres exhibited DBH-LI. There were no detectable differences in DBH-LI with regard to time of day and age of the animals. These results sugest that NA synthesis may be relatively low in intrapineal sympathetic nerve fibers and that the NA required for the regulation of pineal melatonin synthesis may, to a large degree, stem from the circulation. In addition to nerve fibres, some rare intrapineal cell bodies exhibited DBH-LI; in 5-month-old rats their numbers did not reveal significant differences between day and night. These cells do not appear to represent pinealocytes. They may be a special population of noradrenergic nerve cells perhaps belonging to an as yet unknown intrapineal regulatory system.
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  • 5
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By using a plethora of region-specific antisera, this light microscopic immunohistochemical study revealed that derivatives from the three opioid precursors, i.e. proenkephalin, prodynorphin and proopiomelanocortin are differentially distributed in the pineal gland of guinea pig. Various molecular forms of immunoreactive opioid peptides derived from proenkephalin or prodynorphin were prosent in a minority of pinealocytes as well as in nerves. In contrast to this dual distribution pattern of opioid-active peptides, the opioid-inactive derivative from proopiomelanocortin, alpha-melanocyte stimulating hormone, was exclusively present in a large proportion of pinealocytes. A multiple and differential origin and function of opioidergic pineal innervation involving sympathetic, parasympathetic and sensory components is suggested. α-MSH is proposed as a pineal hormone which may act in concert with melatonin to regulate pineal rhythms or may function like MSH of pituitary origin.
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  • 6
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Although some embryological and morphological features speak in favour of a neuronal character of rodent pinealocytes, histochemistry and ultrastructure let this issue appear controversial. Using antibodies to different neurofilaments, the neural adhesion molecule L1, synaptophysin and tubulin as neuronal markers, the pineal glands of rat and guinea-pig were studied by means of immunfluorescence. Neurofilament-immunoreactivity was present in some rat pineal nerve fibers and in the majority of guinea-pig pinealocytes, L1 decorated rat intrapineal nerve fibers, synaptophysin was almost ubiquitously distributed in the pineal of both species, while tubulin-immunofluorescence was seen in nerve fibers of rat and guinea-pig pineal and in some pinealocytes of the latter. These findings speak in favour of the neuronal character of guinea-pig pinealocytes. The lack of neurofilament- and tubulin-immunoreactivity in rat pinealocytes might be attributable to very low concentrations of these proteins or species differences as to their expression. Further studies including in situhybridisation of relevant mRNAs will be necessary to answer these questions definitely.
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  • 7
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung In den Pinealzellen des Meerschweinchens lassen sich histochemisch NADH-, NADPH-Diaphorase, Glucose-6-phosphatdehydrogenase, unspezifische Esterase, alkalische und saure Phosphatase sowie Succinatdehydrogenase nachweisen. Bei den 4 erstgenannten Enzymnachweisen zeichnen sich gruppen oder kettenförmig angeordnete Pinealzellen durch eine besonders starke Enzymaktivität aus. Dieses Hervortreten von Pinealzellgruppen ist bereits bei Feten vorhanden. In der Zirbeldrüse trächtiger Meerschweinchen findet sich in der 2. Hälfte der Gravidität eine starke Aktivitätszunahme der NADH- und NADPH-Diaphorase, die sich etwa am 2. Tag post partum bzw. 2 Tage nach Ovarektomie oder Hysterektomie zurückbildet. Fetektomie allein bleibt wirkungslos. Die für trächtige Tiere typischen Enzymveränderungen lassen sich bei normalen Meerschweinchen weder durch 14tägige Verabreichung von Choriongonadotropin, Östradiol, Progesteron oder Placentahomogenat noch durch Kastration erzeugen.
    Notes: Summary In the pinealocytes of guinea-pigs NADH diaphorase, NADPH diaphorase, glucose-6-phosphate dehydrogenase, nonspecific esterase, alkaline phosphatase, acid phosphatase, and succinate dehydrogenase could be demonstrated histochemically. When stained for NADH diaphorase, NADPH diaphorase, glucose-6-phosphate dehydrogenase, or nonspecific esterase groups of neighbouring pinealocytes show a stronger staining reaction than the rest of the pinealocytes. These differences in stainability are already present in fetal guinea-pigs. In the pineal gland of pregnant guinea-pigs a strong increase of NADH diaphorase and NADPH diaphorase activity is found in the second half of gestation. 2 days after birth or 2 days after oophorectomy or hysterectomy the enzyme activities reverse to normal. Fetectomy alone does not affect the enzyme pattern. In normal guinea-pigs, neither the administration of chorion gonadotrophins, estradiol, progesteron and homogenized placental tissue for 2 weeks nor gonadectomy induce histochemically detectable enzyme changes.
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  • 8
    ISSN: 1432-1106
    Keywords: Magnetic field (effects of) ; Pineal gland ; Serotonin-N-acetyltransferase activity ; Melatonin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study the effects of artificial magnetic fields on pineal serotonin-N-acetyltransferase (NAT) activity and melatonin content in male Sprague-Dawley rats were investigated to study the secretory activity of the pineal gland. Experimental inversion of the horizontal component of the natural magnetic field, performed at night-time, led to a significant decrease of both parameters investigated. During day-time, this effect was less conspicuous. During night-time, inversion of the horizontal component is followed by a reduced pineal secretory activity for about 2 h. After 24 h exposure to the inverted horizontal component, return to the natural condition was followed by a renewed clear depression of pineal NAT activity and melatonin content, indicating that the main stimulus is not the inverted magnetic field itself but rather its change. Changing the inclination of the local magnetic field from 63 ° to 58 °, 68 ° or 78 °, respectively also decreased the secretory activity of the rat pineal gland.
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  • 9
    ISSN: 1432-1106
    Keywords: Rat ; Pineal gland ; Pinealocyte ; Rhythms ; Circadian rhythm ; Electrical activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular single-unit recordings were made during day- and night-time in the pineal gland of urethane-anesthetized adult male Sprague-Dawley rats. All cells exhibiting spontaneous electrical activity had firing frequencies from less than 1 Hz to about 100 Hz, and their discharge patterns were characterized as regular, irregular or bursting. While most of the spontaneously active cells (n=63) showed a uniform activity level throughout the recording period (30–120 min), a group of 9 cells exhibited oscillatory rhythms with periods of 4–8 min. In addition, long-term recordings across day- and night-time from five cells revealed increasing activity during night-time in three cells, while the remaining two units showed constant activity throughout the recording time (8–20 h). Comparison of day- and night-data in general indicated an overall higher level of activity at night.
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  • 10
    ISSN: 1432-1106
    Keywords: Pineal gland ; Synaptic ribbons ; Synaptic spherules ; Melatonin (serum) ; Circadian rhythm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous studies have shown that the “synaptic” bodies of mammalian pinealocytes are a heterogeneous group of organelles. Whereas “synaptic” ribbons (SR) exhibit a day/night rhythm with small numbers during daytime and high numbers at night, the so-called “synaptic” spherules (SS) show species-specific differences in their rhythmicity. In the present study the numbers of SR and SS were monitored in male guinea pigs over a full 24-h period at 4-hourly intervals (LD 12:12, lights on at 7:00). The results obtained show that the rhythms of SR numbers and SS numbers are out of phase by 180°. SR numbers are small during daytime and high at night, whereas SS numbers are high during daytime and low at night. As there are no indications that SR are transformed into SS and vice versa and as SR and SS lie in different parenchymal areas it is suggested that they characterize different types of pinealocytes with differing rhythmicities. — Serum melatonin levels were low during daytime (30 pg/ml) and increased at night to reach a peak (84 pg/ml) at 24:00 h.
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