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At least 325 records · Page 18Linked to original sources

PubMed1990

Sex- and age-dependent nature of the cytoplasmic 5 alpha-dihydrotestosterone (DHT) binding site/receptor in bovine pineal gland.

Recent research has justified the presumption that the pineal gland plays a role in the regulation of the gonadal system in mammals. Evidence also exists for androgen receptors in pinealocytes. In the current study, our approach has been to assess the age- and sex-dependent nature of 5 alpha-DHT receptors in bovine pineal. Although no significant difference was noted between various groups of bulls, cows, peripuberal cows, and calves (male) for pineal weight, the cytoplasmic 5 alpha-DHT binding site/receptor content in the pineal gland differed significantly. While the males had a low androgen receptor concentration in the pineal (46 fmol/pineal), the females showed the highest (442 fmol/pineal). The peripuberal females without calves and calves (male) presented a 5 alpha-DHT receptor content in between (225 fmol/pineal; 138 fmol/pineal). When the data were related to unit weight of pineal tissue, the difference still existed. It is suggested that the concentration of cytoplasmic 5 alpha-DHT receptors reflects the cellular activity and they are inversely related. Further, low cytoplasmic receptors also indicate that most of it is confined to the nuclear sites, as generally suggested for other androgen-dependent tissues. In the light of these suggestions, it is possible that lowest cytosolic 5 alpha-DHT receptor concentration in the males, in reality, reflects a higher degree of cellular function and a high concentration of the receptors in the nuclear site. Similarly, the peripuberal cows and calves perhaps have more cellular activity in the pineal than the mature cows. The current investigation, for the first time, by directly estimating the androgen receptors/binding site in the bovine pineal gland, demonstrates the sex- and age-dependent nature.

Aging↗

PubMed2000

Somatostatin and somatostatin receptors in the pig pineal gland during postnatal development: an immunocytochemical study.

An immunohistochemical study of the pineal gland of the domestic pig was carried out using rabbit antisera raised against synthetic peptide fragments corresponding to different amino acid sequences of the prosomatostatin, the somatostatin-14, and the somatostatin-28 molecule. The study was supplemented by immunohistochemical staining with rabbit antisera raised against five subtypes of somatostatin receptors. The pineal glands were taken from the newborn, 21-day-old and 7-month-old pigs. Immunoreactive nerve fibers and cells were observed in the pineal gland with all the antisera against somatostatin and prosomatostatin. The nerve fibers were located throughout the pineal gland-in the capsule, connective septa, and parenchyma-with the highest density in proximo-ventral part of the gland. The somatostatin positive fibers were also found in the habenular and posterior commissurae areas. Somatostatin-immunoreactive cell bodies were observed mostly in the central part of the gland. These results point to the existence of two somatostatin sources in the pig pineal gland: 1) nerve fibers, probably of central origin; and 2) cells that may represent intrapineal neurons or specialised pinealocytes. A clear difference in the immunoreactivity between newborn, 21-day-old, and 7-month-old pigs was found. Generally, the density of nerve fibers was lower in adult than young animals. The number of the cells also decreased with age. By using the antisera against the five somatostatin receptors, only sst3 - receptor immunoreactivity could be detected. The receptor-immunoreactivity was confined to varicose and smooth fibers and some cells. The sst(3)-receptor positive structures were localised in all parts of the gland and their number was higher in younger pigs.

Animals↗

PubMed1981

Possible hormonal role of the angiotensin-like peptides in mammals' pineal gland.

An isorenin is synthetized in the pineal gland cells. The amount of isorenin as well as the synthesis of angiotensin I and II in the pineal gland depends on the circadian rhythm, osmotic stimuli and stimulation of the cervical sympathetic postganglionar fibres. Pineal angiotensin is released both into the blood and in the cerebrospinal fluid (CFS). The major site of the pineal angiotensin action are the circumventricular organs, the preiventricular receptors of the anterior hypothalamus and the epiphysis cerebri itself. Except its participation in regulating arterial pressure and the hydroelectrolytic metabolism, through its central effects on the brain, pineal angiotensin-like peptides also participate in the pool of circulating angiotensin and it may represent Farrell's pineal glomerulotropic factor.

Angiotensin I↗

PubMed1978

Vascular permeability to proteins and peptides in the mouse pineal gland.

The permeability of fenestrated capillaries in the mouse pineal gland to proteins and peptides was demonstrated by means of ultrastructural tracers. Horseradish peroxidase (HRP) and microperoxidase (MP) were injected intravenously and allowed to circulate for approximately 30 s, 1 min, 5 min, 1 or 2 h. The tissue was then fixed by vascular perfusion or by immersion with aldehydes. In all experiments a pronounced extravasation of HRP and MP occurred. Transendothelial vesicular transport seemed to have occurred across the fenestrated capillaries. The most pronounced tracer labeling of vesicles was found after 1 min of MP- or HRP-circulation. The vesicles were uncoated and more than 70% of the HRP- and MP-containing vesicles exhibited diameters between 50 and 110 nm. Furthermore, three other transcapillary pathways taken by the tracers are suggested: 1) via intercellular junctions, 2) through fenestrae and 3) via channels formed by fusion of vesicles with the luminal and abluminal cell membranes. Based on these results, it is assumed that the capillaries in the mouse pineal gland also permeable to peptides synthesized and secreted by the pineal gland.

Animals↗

PubMed1993

Tissue kallikrein in the rat pineal gland: an immunocytochemical study.

Tissue kallikrein in the rat pineal gland was immunocytochemically investigated with the aid of specific antiserum against rat urinary kallikrein. We also compared the tissue kallikrein immunoreactivity of the pineal gland with that of the submandibular gland and kidney, which have been well established as tissue kallikrein-synthesizing organs. The cytoplasm of pinealocytes from both the superficial and the deep portion of the gland exhibited specific immunolabeling for tissue kallikrein, but the immunoreaction was weaker than that observed in exocrine organs. Two types of tissue kallikrein-immunoreactive pinealocytes were distinguished; the first predominant type displayed moderate immunostaining, whereas a small number of cells, the second type, were so intensely labeled that their cytoplasmic processes were clearly outlined. The results of the present study suggest the existence of different types of pinealocytes and a potential physiological role of tissue kallikrein in the rat pineal gland.

Animals↗

PubMed1975

Nervous connections between the brain and the pineal gland in the cat (Felis catus) and the monkey (Cercopithecus aethiops).

Silver-impregnated series of cat and monkey (Cercopithecus aethiops) brains were studied in an attempt to demonstrate the existence of nervous connections between the brain and the pineal gland via the pineal stalk (central pineal connections). The presence of such connections between both the pineal gland and the habenular area, and between the pineal gland and the posterior commissure was verified in this study. A well defined median nerve tract between the pineal gland and the posterior commissure is described.

Animals↗

PubMedDate not supplied

Peptidergic peripheral nervous systems in the mammalian pineal gland.

The distribution and density of tyrosine hydroxylase (TH) and neuropeptide Y (NPY)-immunoreactive, sympathetic fibers and calcitonin gene-related peptide (CGRP)-, substance P (SP)-, and vasoactive intestinal polypeptide (VIP)-immunoreactive, non-sympathetic fibers in the pineal gland, the effects of superior cervical ganglionectomy (SCGX) on these fibers, and the location of their terminals in the pineal gland were compared between rodents and non-rodents. A dense network of TH/NPY-positive fibers is present all over the pineal gland. A less dense network of CGRP/SP- or VIP-positive fibers occurs in the whole pineal gland of non-rodents, but these fibers are usually confined to the superficial pineal gland in rodents. After SCGX, some TH/NPY-fibers remain only in the deep pineal gland in rodents, whereas considerable numbers of these fibers persist throughout the gland in non-rodents. Thus, the remaining fibers, probably originating from the brain, may be more numerous in non-rodents. Since CGRP-, SP- or VIP-immunoreactive fibers in the pineal capsule can be traced to those in the gland, and since these fibers are ensheathed by Schwann cells, it is concluded that these fibers belong to the peripheral nervous system. However, the existence of SP-positive central fibers cannot be denied in some species. In the superficial pineal gland of rodents, sympathetic terminals are mostly localized in perivascular spaces, whereas the parenchymal innervation by sympathetic fibers in the pineal gland is more dense in non-rodents than in rodents. Synapses between sympathetic nerve terminals and pinealocytes occur occasionally in non-rodents, but only rarely in the superficial pineal gland of rodents. The occurrence of the synapses may depend on the frequency of intraparenchymal sympathetic terminals.

Adrenergic Fibers↗

PubMed1988

The blood vascular architecture of the rat pineal gland: a scanning electron microscopic study of corrosion casts.

The blood vascular bed of the rat pineal gland was reproduced through a low viscosity methacrylate casting medium and observed with a scanning electron microscope. The pineal gland was located in front of the confluens sinuum which was formed by the confluence of the left and right transverse sinuses and the superior sagittal and great cerebral veins. The pineal gland was found to contain a rich vascular network of freely anastomosing capillaries. This network received a few afferent arteries from the posterior cerebral arteries while emitting ten to fifteen efferent veins. Most of these efferent veins drained into the upper segment of the great cerebral vein; the remaining one or two efferent veins continued directly into the confluens sinuum. A marked constriction, probably representing a venous valve or valve-like projection, was observed in the opening area of the great cerebral vein. Circular constrictions, probably representing sphincters, were imprinted in the efferent vessels. No direct vascular connection was noted between the pineal gland and the nervous tissues or between the pineal gland and the choroid plexuses of the third and lateral ventricles.

Animals↗

PubMed1997

Light-induced changes in frog pineal gland N-acetyltransferase activity.

N-Acetyltransferase (NAT) activity was determined in the pineal gland of frogs (Rana tigrina) of different ages using 2-aminofluorene and p-aminobenzoic acid as substrates, and assayed by high-pressure liquid chromatography. Frogs of different ages were either killed during the light phase or exposed to darkness or light for 1 min during the dark phase of the lighting cycle, then returned to their cages in darkness for 30 min before being killed. The pineal gland NAT activity of 1-month-old frogs was inhibited when the animal was nocturnally exposed to 1 min of light. Nocturnal light exposure did not inhibit NAT activity in 1-month-old frogs, even though these animal displayed clear light-dark differences in pineal gland NAT activity. Nocturnal light exposure did not inhibit night-time levels of NAT activity in 1-month-old animals which had been bilaterally enucleated, thus suggesting that this effect is retinally mediated. Pretreatment of 1-month-old and 6-month-old animals with isoproterenol (a beta-adrenoceptor agonist drug) prevented the nocturnal light-induced inhibition of NAT activity. From the different sensitivity of 1-month-old and 6-month-old animals to different intensities or durations of nocturnal light exposure it was found that the duration or intensity of light exposure was not able to inhibit nocturnal NAT activity. The NAT activity was at least 4-5-fold greater in 1-month-old frogs than in 6-month-old frogs. This is the first demonstration of the retino-pineal gland pathway that appears to produce light-induced changes in pineal glands of frogs 1-month-old or older, but this pathway only functions in 1-month-old frogs, and does not appear to function in 6-month-old frogs.

Aging↗

PubMed1983

Morphological findings relating to the problem of cortex and medulla in the pineal glands of rat and hamster.

Because, in previous investigations on the rat pineal gland, karyometric studies of pinealocytes from cortical and medullary regions had yielded contradictory results, experiments were carried out to resolve this problem. In immersion-fixed, paraffin-embedded pineal glands, nuclear size of cortical regions was invariably larger than that in the medulla, the nuclear size clearly depending on the plane of sectioning. The differences between cortex and medulla were abolished in (a) pineal glands sagittally bisected prior to immersion fixation and (b) perfusion-fixed, epoxy resin-embedded pineal tissue, suggesting that unequal pinealocyte nuclear size in cortex and medulla is artefactual. In the hamster pineal gland, cortical and medullary regions are separated by a narrow band of interstitial cells, indicating that different structural features account for this subdivision in different species.

Animals↗

PubMed1989

Presence of a metallothionein-like protein in the bovine pineal gland.

The high concentration of zinc in the bovine pineal gland prompted us to investigate the existence of a zinc-binding protein in this organ. In this study, we report that the subcellular distribution of zinc in the bovine pineal gland is nonuniform, with the crude nuclear, mitochondrial, microsomal, and supernatant fractions having 0.264 +/- 0.038, 0.160 +/- 0.019, 0.130 +/- 0.016, and 0.287 +/- 0.010 micrograms zinc/mg protein, respectively. Furthermore, gel filtration studies using Sephadex G-75 and a 105,000 g supernatant fraction revealed two zinc binding protein peaks that bind 1.7 and 3.7 micrograms Zn++/mg protein, respectively. Furthermore, purification of the protein peak with an elution volume (ve/vo) of 2.06 on anion exchange chromatography (DEAE-A25) yielded a single protein peak which binds 10 micrograms zinc/mg protein. The comparative high performance liquid chromatographic (HPLC) profiles of the zinc-induced hepatic metallothionein isoform I (retention time = 17.39 min) and of the bovine pineal metallothionein-like protein isoform I (retention time = 17.49 min) are similar. Since zinc is a potent inhibitor of sulfhydryl-containing enzymes and receptor sites, we investigated the effects of zinc and found that it inhibited the binding of [3H]glutamate (IC 50 = 80 microM) and of [3H]spiroperidol (IC 50 = 0.6 mM) to the pineal membranes. The results of these studies are interpreted to indicate that the bovine pineal gland possesses an active and dynamic zinc homeostatic mechanism, whose precise function(s) remain(s) to be delineated.

Animals↗

PubMed1977

Influence of psoralen on melatonin formation in rat pineal gland in organ culture.

8-Methoxypsoralen (10(-4) M) added to the medium of rat pineal glands in organ culture induces a five-fold increase of 14C-labelled N-acetylserotonin and melatonin formation when serotonin is used as 14C-labelled precursor. Addition of d-amphetamine (10(-5) M) to pineal glands also results in an increase of N-acetylserotonin and melatonin formation. This increase is enhanced by the addition of 8-methoxypsoralen (10(-5) M). In pineal glands pre-incubated for 24 h 8-methoxypsoralen (10(-4) M) caused an increased production of N-acetylserotonin and melatonin. This indicates that the effect of 8-methoxypsoralen is mediated through a postsynaptic event and not by release of noradrenaline or blocked re-uptake of amines to nerve terminals in the pineal gland. Further studies of the clinical significance of the effect of psoralen on pineal gland metabolism seems warranted.

Animals↗

PubMed1987

Morphology of the pineal gland in pregnant and nursing sows.

The pineal glands of pregnant and nursing sows were studied by light and electron microscopy. Similar structural changes in the pineal gland during pregnancy and lactation were noted as follows: a proliferation of glial cells concurrent with a decrease in the number of pinealocytes, a relative increase in the number of pinealocytes with cytoplasmic accumulation of dense bodies, and an increase in number of presumptive microglia. It appears that pregnancy and lactation exert a complex influence on pineal function, with a predominantly stimulating effect.

Animals↗

PubMed1997

Circannual somatostatin gene and somatostatin receptor gene expression in the early post-natal rat pineal gland.

The origin of somatostatin in the pineal gland is controversial as a double origin - neural in pinealopetal nerve fibers and parenchymal corresponding to locally synthesized peptide - is suggested. We have investigated the ontogeny and possible circadian and circannual variations of somatostatin and somatostatin receptor gene expression in the rat pineal gland using RT-PCR. Somatostatin gene expression was observed in the pineal of animals up to 15 days of postnatal life in autumn and winter, but not in prepubertal or adult rats; no transcript was detected during spring and summer at any age and a circadian rhythm was only detected in 15-day-old rats. In situ hybridization confirmed these results. The transcript of the somatostatin receptor gene (SSTR2) was detected at all ages studied with no seasonal variations in its expression, indicating separate regulatory mechanisms. In conclusion, somatostatin and somatostatin receptor mRNAs are expressed in the neonatal rat pineal with circadian and seasonal variations.

Animals↗

PubMed1999

Does the pineal gland play a role in neuroendocrine fear responses?

The pineal gland secretes melatonin under an influence of suprachiasmatic nucleus neurones. Pinealectomy or melatonin administration affects behavioural responses to novel stimuli. Fear or novel stimuli inhibit vasopressin (VP) and facilitate oxytocin (OT) or prolactin (PRL) release from the pituitary. Thus the suprachiasmatic nucleus-pineal gland system may modulate VP, OT and PRL responses to conditioned fear stimuli. In the present experiments with male rats, pinealectomy or melatonin administration did not significantly change VP, OT or PRL responses to conditioned fear stimuli. Electrolytic lesions of the suprachiasmatic nuclei impaired VP but not OT or PRL responses. The results show that the pineal gland is not involved in neuroendocrine responses to conditioned fear stimuli and suggest that the suprachiasmatic nucleus is necessary for the VP response to fear stimuli.

Animals↗

PubMed1979

Hypothalamus-pituitary-thyroid axis interactions with pineal gland in the rat.

We examined in the rat several possible relationships between the pineal gland and the hypothalamus-pituitary-thyroid axis. The pineal gland, the retina, and the hypothalamus exhibited a diurnal rhythm in thyrotropin-releasing hormone (TRH) content with peak values occurring around 1200 h. This rhythm in the hypothalamus was abolished by constant light but was not affected by pinealectomy. Nor did pinealectomy affect hypothalamic TRH content, pituitary content of thyroid-stimulating hormone (TSH) or prolactin; serum levels of (TSH), triiodothyronine (T3), or thyroxine (T4), or serum free-thyroxine index; or free-triiodothyronine index. Melatonin did not affect TSH or prolactin release from the anterior pituitary or TRH release from the hypothalamus in vitro. Isoproterenol did not affect the TRH content of pineal glands in vitro; nor did TRH or T3 affect basal or stimulated activities of serotonin N-acetyltransferase, the presumed controlling enzyme in melatonin production. We found no evidence for significant interactions between the pineal gland and the hypothalamus-pituitary-thyroid axis.

Animals↗

PubMed2006

The perivascular phagocyte of the mouse pineal gland: an antigen-presenting cell.

The perivascular space of the rat pineal gland is known to contain phagocytic cells that are immunoreactive for leukocyte antigens, and thus they appear to belong to the macrophage/microglial cell line. These cells also contain MHC class II proteins. We investigated this cell type in the pineal gland of mice. Actively phagocytosing cells with a prominent lysosomal system were found in the pericapillary spaces of the mouse pineal gland following intravenous injection of horseradish peroxidase. The cells also exhibited strong acid phosphatase activity. Perivascular cells were immunopositive for MHC class II protein and for CD68, a marker of monocytes/phagocytes. This study verifies that perivascular phagocytes with antigen-presenting properties are present in the mouse pineal gland.

Acid Phosphatase↗

PubMed2003

Melatonin-secreting pineal gland: a novel tissue source for neural transplantation therapy in stroke.

Chronic systemic melatonin treatment attenuates abnormalities produced by occlusion of middle cerebral artery (MCA) in adult rats. Because the pineal gland secretes high levels of melatonin, we examined in the present study whether transplantation of pineal gland exerted similar protective effects in MCA-occluded adult rats. Animals underwent same-day MCA occlusion and either intrastriatal transplantation of pineal gland (harvested from 2-month-old rats) or vehicle infusion. Behavioral tests (from day of surgery to 3 days posttransplantation) revealed that transplanted stroke rats displayed significantly less motor asymmetrical behaviors than vehicle-infused stroke rats. Histological analysis at 3 days posttransplantation revealed that transplanted stroke rats had significantly smaller cerebral infarction than vehicle-infused rats. Additional experiments showed that pinealectomy affected transplantation outcome, in that transplantation of pineal gland only protected against stroke-induced deficits in stroke animals with intact pineal gland, but not in pinealectomized stroke rats. Interestingly, nonpinealectomized vehicle-infused stroke rats, as well as pinealectomized transplanted stroke rats, had significantly lower melatonin levels in the cerebrospinal fluid than nonpinealectomized transplanted stroke rats. We conclude that intracerebral transplantation of pineal gland, in the presence of host intact pineal gland, protected against stroke, possibly through secretion of melatonin.

Animals↗