Search results for "Pineal gland"
showing 10 items of 143 documents
24-hour-variation of pineal gland volume, pinealocyte nuclear volume and mitotic activity in male Sprague-Dawley rats
1983
In two experiments carried out on two alternate days, the 24-h-rhythmicity of pineal gland volume, pinealocyte nuclear size in cortex and medulla and mitotic activity were studied in male Sprague-Dawley rats, to assess to what extent morphological parameters reflect the pronounced day/night differences in pineal melatonin formation. Pineal volume exhibited statistically significant changes in the second experiment only, with a distinct trough at 6 p.m. Karyometry revealed highly variable patterns. In the first experiment, pinealocyte nuclear changes lacked parallelism in cortex and medulla. The cortex exhibited a bimodal curve with peaks at noon of the first day and at 6 a.m. of the second …
Tentative immunohistochemical demonstration of melatonin in the rat pineal gland
1977
In the present study an attempt was made to demonstrate melatonin in the rat pineal gland by means of immunohistochemistry. The anti-body used was raised against 5-methoxy-N-acetyltryptophan which is chemically similar to melatonin. Specific fluorescence was demonstrable only in pineals from rats killed during the night, when melatonin formation is high. It was restricted to parenchymal cells lying in a marginal zone of the organ. These results are discussed in relation to a subdivision of the pineal parenchyma into cortical and medullary areas.
Circadian and photoperiodic correlation between the number of pineal gland synaptic ribbons and serum melatonin levels in the rat.
1987
A study is made of the number of pineal gland synaptic ribbons in 35 maleWistar rats over a 24-hour period during the months of September and February, in correlation to the serum melatonin levels during the same periods and photophases.The results of the study confirm those reported by others authors and suggest that the synaptic ribbons may be the stimuli-transmitting organs facilitating pineal secretory function.
Neuropeptide Y: distribution of immunoreactivity and quantitative analysis in diencephalic structures and cerebral cortex of dwarf hamsters under dif…
1995
The distribution of neuropeptide Y-like immunoreactivity (NPY-LI) was investigated by immunohistochemistry and radioimmunoassay (RIA) in the brain of the Djungarian hamster (Phodopus sungorus) held under either long or short photoperiods. In the diencephalic and telencephalic structures studied, distinct patterns of NPY-LI were basically consistent in male and female animals of both groups. NPY levels detected by RIA from tissue samples taken at six time points throughout the 24-hour cycle were in the range of 15-60 pmol/mg protein in the diencephalon or below 5 pmol/mg protein in cerebral cortex. In the diencephalon, immunoreactive structures were seen in the preoptic, peri- and paraventri…
Atypical 24-hour rhythms of serotonin N-acetyltransferase activity in the rat pineal gland.
1988
Previous long-term studies have shown that in the pineal gland of rats melatonin synthesis is subject to infradian rhythms with periods between 4 and 7 days. Since in these studies melatonin-related parameters were measured at one timepoint of a 24-hr cycle only, the aim of the present investigation was to extend these experiments by more frequent sampling, to characterize the infradian rhythmicity in more detail. Male Sprague-Dawley rats kept under a light schedule of LD 12:12 (lights on at 0700) were killed at 6-hr intervals on 8 consecutive days. After decapitation the pineal gland was rapidly dissected out, followed by measurements of one of the melatonin-forming enzymes, serotonin N-ac…
Immunohistochemical evidence for the presence of peptides derived from proenkephalin, prodynorphin and proopiomelanocortin in the guinea pig pineal g…
1988
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 present 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 differ…
Synaptic ribbons of the rat pineal gland: responses to in-vivo and in-vitro treatment with inhibitors of protein synthesis.
1990
To elucidate the role of protein synthesis in the nocturnal increase of synaptic ribbons in the rat pineal gland, actinomycin-D, which inhibits transcription, and cycloheximide, an inhibitor of translation, were used. To assure that the drugs were effective and to relate morphological changes to pineal biosynthetic phenomena, the activity of N-acetyltransferase and levels of pineal indoleamine were measured. Results of in-vivo, short-term and long-term treatment with either drug suggest that transcription of proteins related to synaptic ribbon formation occurs during the first half of the light phase, whereas translation takes place during the first few hours of the dark phase. In contrast,…
Effects of chemical and surgical ganglionectomy on electrical activity of the pineal gland of male rats.
1986
In order to elucidate further the role of sympathetic innervation for pineal function, the influence of sympathectomy on the spontaneous electrical activity of single cells in the pineal gland of adult male rats was investigated. Extracellular single-unit recordings were made during nighttime in the pineal gland of urethane-anesthetized, blinded adult male rats that had been treated neonatally with 6-hydroxydopamine, or that were ganglionectomized either during, or 12-16 h or 36-40 h, prior to the recording experiment. These experiments revealed that the excitatory influence of the sympathetic system on pineal nocturnal electrical activity can be abolished by either chemical sympathectomy o…
Fos-related antigen 2 (Fra-2) memorizes photoperiod in the rat pineal gland
2004
As the physiological role of fos-related antigen-2 (Fra-2) is largely unknown and since the pineal plays an important role in the photoperiodic control of the body, we have tested the hypothesis that Fra-2 expression is photoperiod-dependent and may be involved in imprinting photoperiod on the pineal gland and the body as a whole. To this end, we have investigated Fra-2 mRNA expression and Fra-2 protein expression under various light/dark (LD) cycles. A clear nocturnal increase occurs for both monitored parameters under all photoperiodic conditions studied. The level of Fra-2 protein expression clearly depends on photoperiod, because the amount of protein at dark onset and during the night …
The photoperiod entrains the molecular clock of the rat pineal.
2005
The suprachiasmatic nucleus-pineal system acts as a neuroendocrine transducer of seasonal changes in the photoperiod by regulating melatonin formation. In the present study, we have investigated the extent to which the photoperiod entrains the nonself-cycling oscillator in the Sprague-Dawley rat pineal. For this purpose, the 24-h expression of nine clock genes (bmal1, clock, per1, per2, per3, cry1, cry2, dec1 and dec2) and the aa-nat gene was monitored under light-dark 8 : 16 and light-dark 16 : 8 in the rat pineal by using real-time RT-PCR. The 24-h pattern of the expression of only per1, dec2 and aa-nat genes was affected by photoperiod. In comparison with the short photoperiod, the durat…