Showing papers on "Pinealocyte published in 2013"

Immune-pineal axis: nuclear factor κB (NF-kB) mediates the shift in the melatonin source from pinealocytes to immune competent cells

Abstract: Pineal gland melatonin is the darkness hormone, while extra-pineal melatonin produced by the gonads, gut, retina, and immune competent cells acts as a paracrine or autocrine mediator. The well-known immunomodulatory effect of melatonin is observed either as an endocrine, a paracrine or an autocrine response. In mammals, nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) blocks noradrenaline-induced melatonin synthesis in pinealocytes, which induces melatonin synthesis in macrophages. In addition, melatonin reduces NF-κB activation in pinealocytes and immune competent cells. Therefore, pathogen- or danger-associated molecular patterns transiently switch the synthesis of melatonin from pinealocytes to immune competent cells, and as the response progresses melatonin inhibition of NF-κB activity leads these cells to a more quiescent state. The opposite effect of NF-κB in pinealocytes and immune competent cells is due to different NF-κB dimers recruited in each phase of the defense response. This coordinated shift of the source of melatonin driven by NF-κB is called the immune-pineal axis. Finally, we discuss how this concept might be relevant to a better understanding of pathological conditions with impaired melatonin rhythms and hope it opens new horizons for the research of side effects of melatonin-based therapies.

The pineal gland from development to function.

Abstract: The pineal gland is a small neuroendocrine organ whose main and most conserved function is the nighttime secretion of melatonin. In lower vertebrates, the pineal gland is directly photosensitive. In contrast, in higher vertebrates, the direct photosensitivity of the pineal gland had been lost. Rather, the action of this gland as a relay between environmental light conditions and body functions involves reception of light information by the retina. In parallel to this sensory regression, the pineal gland (and its accessory organs) appears to have lost several functions in relation to light and temperature, which are important in lower vertebrate species. In humans, the functions of the pineal gland overlap with the functions of melatonin. They are extremely widespread and include general effects both on cell protection and on more precise functions, such as sleep and immunity. Recently, the role of melatonin has received a considerable amount of attention due to increased cancer risk in shift workers and the discovery that patients suffering from neurodegenerative diseases, autism, or depression exhibit abnormal melatonin rhythms.

Role of melatonin and its receptors in the vertebrate retina.

Abstract: Melatonin is a chemical signal of darkness that is produced by retinal photoreceptors and pinealocytes. In the retina, melatonin diffuses from the photoreceptors to bind to specific receptors on a variety of inner retinal neurons to modify their activity. Potential target cells for melatonin in the inner retina are amacrine cells, bipolar cells, horizontal cells, and ganglion cells. Melatonin inhibits the release of dopamine from amacrine cells and increases the light sensitivity of horizontal cells. Melatonin receptor subtypes show differential, cell-specific patterns of expression that are likely to underlie differential functional modulation of specific retinal pathways. Melatonin potentiates rod signals to ON-type bipolar cells, via activation of the melatonin MT2 (Mel1b) receptor, suggesting that melatonin modulates the function of specific retinal circuits based on the differential distribution of its receptors. The selective and differential expression of melatonin receptor subtypes in cone circuits suggest a conserved function for melatonin in enhancing transmission from rods to second-order neurons and thus promote dark adaptation.

Melatonin synthesis in human colostrum mononuclear cells enhances dectin‐1‐mediated phagocytosis by mononuclear cells

Abstract: Many cells in the organism besides pinealocytes, synthesize melatonin. Here, we evaluate both the mechanism of zymosan-induced melatonin synthesis and its autocrine effect in human colostral mononuclear cells. The synthesis of melatonin was induced by activation of the transcription factor nuclear factor kappa B (NF-κB), as either the blockade of the proteasome or the binding of NF-κB to DNA inhibits zymosan-induced melatonin synthesis. As observed in RAW 264.7 lineage cells, the dimer involved is RelA/c-Rel. Melatonin plays a direct role in mononuclear cell activity, increasing zymosan-induced phagocytosis by stimulating MT2 melatonin receptors and increasing the expression of dectin-1. This role was confirmed by the blockade of melatonin receptors using the competitive antagonist luzindole and the MT2 -selective partial agonist 4P-PDOT. In summary, we show that melatonin produced by immune-competent cells acts in an autocrine manner, enhancing the clearance of pathogens by increasing phagocyte efficiency. Given that these cells are present in human colostrum for 4 or 5 days after birth, this mechanism may be relevant for the protection of infant health.

Chronobiology of Melatonin beyond the Feedback to the Suprachiasmatic Nucleus—Consequences to Melatonin Dysfunction

Abstract: The mammalian circadian system is composed of numerous oscillators, which gradually differ with regard to their dependence on the pacemaker, the suprachiasmatic nucleus (SCN). Actions of melatonin on extra-SCN oscillators represent an emerging field. Melatonin receptors are widely expressed in numerous peripheral and central nervous tissues. Therefore, the circadian rhythm of circulating, pineal-derived melatonin can have profound consequences for the temporal organization of almost all organs, without necessarily involving the melatonin feedback to the suprachiasmatic nucleus. Experiments with melatonin-deficient mouse strains, pinealectomized animals and melatonin receptor knockouts, as well as phase-shifting experiments with explants, reveal a chronobiological role of melatonin in various tissues. In addition to directly steering melatonin-regulated gene expression, the pineal hormone is required for the rhythmic expression of circadian oscillator genes in peripheral organs and to enhance the coupling of parallel oscillators within the same tissue. It exerts additional effects by modulating the secretion of other hormones. The importance of melatonin for numerous organs is underlined by the association of various diseases with gene polymorphisms concerning melatonin receptors and the melatonin biosynthetic pathway. The possibilities and limits of melatonergic treatment are discussed with regard to reductions of melatonin during aging and in various diseases.

Homeobox Genes in the Rodent Pineal Gland: Roles in Development and Phenotype Maintenance

Abstract: The pineal gland is a neuroendocrine gland responsible for nocturnal synthesis of melatonin. During early development of the rodent pineal gland from the roof of the diencephalon, homeobox genes of the orthodenticle homeobox (Otx)- and paired box (Pax)-families are expressed and are essential for normal pineal development consistent with the well-established role that homeobox genes play in developmental processes. However, the pineal gland appears to be unusual because strong homeobox gene expression persists in the pineal gland of the adult brain. Accordingly, in addition to developmental functions, homeobox genes appear to be key regulators in postnatal phenotype maintenance in this tissue. In this paper, we review ontogenetic and phylogenetic aspects of pineal development and recent progress in understanding the involvement of homebox genes in rodent pineal development and adult function. A working model is proposed for understanding the sequential action of homeobox genes in controlling development and mature circadian function of the mammalian pinealocyte based on knowledge from detailed developmental and daily gene expression analyses in rats, the pineal phenotypes of homebox gene-deficient mice and studies on development of the retinal photoreceptor; the pinealocyte and retinal photoreceptor share features not seen in other tissues and are likely to have evolved from the same ancestral photodetector cell.

Modulation of pineal melatonin synthesis by glutamate involves paracrine interactions between pinealocytes and astrocytes through NF-κB activation.

Abstract: The glutamatergic modulation of melatonin synthesis is well known, along with the importance of astrocytes in mediating glutamatergic signaling in the central nervous system. Pinealocytes and astrocytes are the main cell types in the pineal gland. The objective of this work was to investigate the interactions between astrocytes and pinealocytes as a part of the glutamate inhibitory effect on melatonin synthesis. Rat pinealocytes isolated or in coculture with astrocytes were incubated with glutamate in the presence of norepinephrine, and the melatonin content, was quantified. The expression of glutamate receptors, the intracellular calcium content and the NF-κB activation were analyzed in astrocytes and pinealocytes. TNF-α's possible mediation of the effect of glutamate was also investigated. The results showed that glutamate's inhibitory effect on melatonin synthesis involves interactions between astrocytes and pinealocytes, possibly through the release of TNF-α. Moreover, the activation of the astrocytic NF-κB seems to be a necessary step. In astrocytes and pinealocytes, AMPA, NMDA, and group I metabotropic glutamate receptors were observed, as well as the intracellular calcium elevation. In conclusion, there is evidence that the modulation of melatonin synthesis by glutamate involves paracrine interactions between pinealocytes and astrocytes through the activation of the astrocytic NF-κB transcription factor and possibly by subsequent TNF-α release.

Circadian clock gene Per2 is not necessary for the photoperiodic response in mice.

Abstract: In mammals, light information received by the eyes is transmitted to the pineal gland via the circadian pacemaker, i.e., the suprachiasmatic nucleus (SCN). Melatonin secreted by the pineal gland at night decodes night length and regulates seasonal physiology and behavior. Melatonin regulates the expression of the β-subunit of thyroid-stimulating hormone (TSH; Tshb) in the pars tuberalis (PT) of the pituitary gland. Long day-induced PT TSH acts on ependymal cells in the mediobasal hypothalamus to induce the expression of type 2 deiodinase (Dio2) and reduce type 3 deiodinase (Dio3) that are thyroid hormone-activating and hormone-inactivating enzymes, respectively. The long day-activated thyroid hormone T3 regulates seasonal gonadotropin-releasing hormone secretion. It is well established that the circadian clock is involved in the regulation of photoperiodism. However, the involvement of the circadian clock gene in photoperiodism regulation remains unclear. Although mice are generally considered non-seasonal animals, it was recently demonstrated that mice are a good model for the study of photoperiodism. In the present study, therefore, we examined the effect of changing day length in Per2 deletion mutant mice that show shorter wheel-running rhythms under constant darkness followed by arhythmicity. Although the amplitude of clock gene (Per1, Cry1) expression was greatly attenuated in the SCN, the expression profile of arylalkylamine N-acetyltransferase, a rate-limiting melatonin synthesis enzyme, was unaffected in the pineal gland, and robust photoperiodic responses of the Tshb, Dio2, and Dio3 genes were observed. These results suggested that the Per2 clock gene is not necessary for the photoperiodic response in mice.

Leptin modulates norepinephrine-mediated melatonin synthesis in cultured rat pineal gland.

Abstract: Pineal melatonin synthesis can be modulated by many peptides, including insulin. Because melatonin appears to alter leptin synthesis, in this work we aimed to investigate whether leptin would have a role on norepinephrine- (NE-)mediated melatonin synthesis in cultured rat pineal glands. According to our data, cultured rat pineal glands express leptin receptor isoform b (Ob-Rb). Pineal expression of Ob-Rb mRNA was also observed in vivo. Administration of leptin (1 nM) associated with NE (1 µM) reduced melatonin content as well as arylalkylamine-N-acetyl transferase (AANAT) activity and expression in cultured pineal glands. Leptin treatment per se induced the expression of STAT3 in cultured pineal glands, but STAT3 does not participate in the leptin modulation of NE-mediated pineal melatonin synthesis. In addition, the expression of inducible cAMP early repressor (ICER) was further induced by leptin challenge when associated with NE. In conclusion, leptin inhibition of pineal melatonin synthesis appears to be mediated by a reduction in AANAT activity and expression as well as by increased expression of Icer mRNA. Peptidergic signaling within the pineal gland appears to be one of the most important signals which modulates melatonin synthesis; leptin, as a member of this system, is not an exception.

Melatonin after Four Decades: An Assessment Of Its Potential

Abstract: 1. Melatonin - without the hype. 2. Serotonin N-acetyltransferase: a personal historical perspective. 3. Evolution of melatonin-producing pinealocytes. 4. Melatonin biosynthesis in chicken retina.5. Ultraviolet light suppresses melatonin biosynthesis in chick pineal gland. 6. Effects of vasoactive intestinal peptide and histamine on melatonin and cAMP production in chick embryo pineal cells. 7. Ceramide inhibits L-type calcium channel currents in rat pinealocytes. 8. Expression of melatonin receptors and 2-(125I)Iodomelatonin binding sites in the pituitary of a teleost fish. 9. Melatonin release from the pineals of two sparids. 10. Photoendocrine signal transduction in pineal photoreceptors of the trout. 11. Intrinsic glutaminergic system negatively regulates melatonin synthesis in mammalian pineal gland. 12. Synaptic vesicle protein SV2B, but not SV2A, is predominantly expressed and associated with microvesicles in rat pinealocytes. 13. Neuropeptide Y (NPY) and NPY receptors in the rat pineal gland. 14. Signal transduction in the rodent pineal organ. 15. Regulation of melatonin synthesis in the ovine pineal gland. 16. Melatonin modulation of prolactin and gonadotrophin secretion. 17. The Siberian hamster as a model for study of the mammalian photoperiodic mechanism. 18. How does the melatonin receptor decode a photoperiodic signal in the pars tuberalis? 19. Daily and circadian expression patterns of mt1 melatonin receptor mRNA in the rat pars tuberalis. 20. Molecular pharmacology and function of melatonin receptor subtypes. 36 more chapters.

Melatonin as a therapeutic factor in gastric ulcer healing under experimental diabetes

Abstract: Melatonin (N-acetyl-5-methoxytryptamine) is a hormon secreted mostly by the pineal gland in the brain which maintains the body's circadian rhythm. Interestingly, this indol derivative is produced by enterochromaffin-like cells (ECL) in the gastrointestinal tract (GIT) in amount about 400 fold greater than detected in the pinealocytes. Previous studies revealed that melatonin exerts beneficial action against acute gastric damage induced by stress ethanol, aspirin and ischemia-reperfusion. Hyperglycemia, which is the main symptom of diabetes mellitus, is known to induce mitochondrial dysfunction and endoplasmic reticulum stress, both promoting the generation of reactive oxygen species (ROS). ROS were shown to exhibit higher activity than molecular oxygen under basal conditions due to unpaired electron in its outermost shell of electrons. ROS lead to damage of cellular proteins, nucleic acids and membrane polyunsaturated fatty lipids. In this study, we induced diabetes mellitus by the application of strep. tozocin in presence of gastric ulcers. Male Wistar rats were used in this model. 9 days after gastric ulcers and diabetes mellitus induction, groups of rats were treated with saline or melatonin (20 mg/kg i.g.). At the termination of the experiment, rats were anesthetized, abdomen was opened and gastric blood flow (GBF) was measured. Stomachs were removed for determination of gastric ulcers area by planimetry. Tissue samples were collected for biochemical assays. We demonstrated that melatonin significantly accelerates gastric ulcers healing with and without coexistence of diabetes mellitus. This effect was accompanied by increase of GBF level. Moreover, we observed an increase in superoxide dismutase (SOD) activity and an decrease in lipid peroxidation products concentration within gastric tissue homogenates of animals treated with melatonin, as compared with control group. Melatonin application accelerates gastric ulcers healing with and without presence of diabetes mellitus. We conclude that melatonin can physiologically regulate anti-oxidative enzymes activity and increase GBF level.

Developmental and diurnal expression of the synaptosomal-associated protein 25 (Snap25) in the rat pineal gland.

Abstract: Snap25 (synaptosomal-associated protein) is a 25 kDa protein, belonging to the SNARE-family (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) of proteins, essential for synaptic and secretory vesicle exocytosis. Snap25 has by immunohistochemistry been demonstrated in the rat pineal gland but the biological importance of this is unknown. In this study, we demonstrate a high expression of mRNA encoding Snap25 in all parts of the rat pineal complex, the superficial-, and deep-pineal gland, as well as in the pineal stalk. Snap25 showed a low pineal expression during embryonic stages with a strong increase in expression levels just after birth. The expression showed no day/night variations. Neither removal of the sympathetic input to the pineal gland by superior cervical ganglionectomy nor bilateral decentralization of the superior cervical ganglia significantly affected the expression of Snap25 in the gland. The pineal expression levels of Snap25 were not changed following intraperitoneal injection of isoproterenol. The strong expression of Snap25 in the pineal gland suggests the presence of secretory granules and microvesicles in the rat pinealocyte supporting the concept of a vesicular release. At the transcriptional level, this Snap25-based release mechanism does not exhibit any diurnal rhythmicity and is regulated independently of the sympathetic nervous input to the gland.

주기적 리듬 조절에 의한 멜라토닌 생산과 생리적 기능의 중요성

Abstract: Circadian rhythm is controlled by hormonal oscillations governing the physiology of all living organisms In mammals, the main function of the pineal gland is to transform the circadian rhythm generated in the hypothalamic suprachiasmatic nucleus into rhythmic signals of circulating melatonin characterized by a largely nocturnal increase that closely reflects the duration of night time The pineal gland has lost direct photosensitivity, but responds to light via multi-synaptic pathways that include a subset of retinal ganglion cells Rhythmic control is achieved through a tight coupling between environmental lighting and arylalkylamine-N-acetyltransferase (AANAT) expression, which is the rhythmcontrolling enzyme in melatonin synthesis Previous studies on the nocturnal expression of AANAT protein have described transcriptional, post-transcriptional, and post-translational regulatory mechanisms Molecular mechanisms for dependent AANAT expression provide novel aspects for melatonin’s circadian rhythmicity Extensive animal research has linked pineal melatonin for the expression of seasonal rhythmicity in many mammalian species to the modulation of circadian rhythms and to sleep regulation It has value in treating various circadian rhythm disorders, such as jet lag or shift-work sleep disorders Melatonin, also, in a broad range of effects with a significant regulation influences many of the body’s physiological functions In addition, this hormone is known to influence reproductive, cardiovascular, and immunological regulation as well as psychiatric disorders

MORPHOLOGY OF THE PINEAL GLAND OF THE ONE HUMPED CAMEL (Camelus dromedaries)

Abstract: The pinealocytes of the pineal gland of the young, middle age and old age camels were studied at light microscopic level. The pineal gland consisted of a wide, triangular, superficially localized distal part and a narrow, elongated proximal part, attached via the choroid plexus to the inter commissural region of the diencephalon. The accessory pineal tissue was localized caudally to the choroid plexus. The pinealocytes were classified into light and dark cells on the basis of their shape, nuclear infoldings, cytoplasmic contents and staining density. The dark cells out-numbered the light cells, however, both of them showed thin cytoplasmic processes. The light cells have round or oval cell bodies and nuclei. The large dark cells showed more variations in their shape in addition to the cytoplasmic pigments. The small cells displayed extremely thin and elongated cell bodies.

Comparative histomorphological study of the pineal gland in human and fowl

Abstract: Objectives : Comparative histological studies of pineal gland of man and fowl has been made to observe structural differences if any between these two species. Background : Some works have been done sporadically on laboratory animals and on birds and also in human correlating with other parameters. In this investigation an approach has been made to observe the cellular organization of the pineal gland parenchyma in these two vertebrates, having different physiological aspects. Methods: Some special stains were used to observe connective tissue elements (Reticulin,collagen and elastic fibers) along with conventional H and E stains. Result and conclusion: The lobular character of the gland, connective tissue septa, shape and size of the pinealocytes were found to be almost common in both species. Major differences seen in fowl pineal gland are the presence of ependymal cells on the walls of the lumen of the lobules and absence of corpora arenacea.

Activation of phospholipase C mimics the phase shifting effects of light on melatonin rhythms in retinal photoreceptors.

Abstract: Many aspects of retinal photoreceptor function and physiology are regulated by the circadian clocks in these cells. It is well established that light is the primary stimulus that entrains these clocks; yet, the biochemical cascade(s) mediating light’s effects on these clocks remains unknown. This deficiency represents a significant gap in our fundamental understanding of photoreceptor signaling cascades and their functions. In this study, we utilized re-aggregated spheroid cultures prepared from embryonic chick retina to determine if activation of phospholipase C in photoreceptors in the absence of light can phase shift the melatonin secretion rhythms of these cells in a manner similar to that induced by light. We show that spheroid cultures rhythmically secrete melatonin and that these melatonin rhythms can be dynamically phase shifted by exposing the cultures to an appropriately timed light pulse. Importantly, we show that activation of phospholipase C using m-3M3FBS in the absence of light induces a phase delay in photoreceptor melatonin rhythms that mirrors that induced by light. The implication of this finding is that the light signaling cascade that entrains photoreceptor melatonin rhythms involves activation of phospholipase C.

Hypophysis -Epiphyseal Interactions: Effects of Corticotropin on Metabolism of Serotonin and Formation of a Melatonin Night-Time Peak

Abstract: In experiments on Wistar mature male rats, we studied the effects of injections of corticotropin (ACTH; single or five daily introductions, 1 U per day) on metabolism of epiphyseal serotonin. Injections of ACTH intensified the process of formation of a night-time peak of melatonin synthesis in the epiphysis at the expense of enhancement of utilization of tryptophan by pinealocytes and its subsequent transformation into serotonin, as well as of intensification of reactions of N-acetylation and subsequent O-methylation of the latter. The observed changes are considered an analog of the defense reaction of the organism to the negative action of an excess of hormones of the hypophyseal-adrenocortical axis in stress.

Effect of Sympathetic ganglionectomy on the Pineal Gland in Rhesus Monkey

Abstract: The light microscopic structure and the effect of superior cervical ganglionectomy on the pineal gland of Rhesus monkey was studied in 24 animals. The animals were divided into three groups. Group I normal controls, Group II after unilateral and Group III after bilateral ganglionectomy. The animals in group II were sacrificed 15 days and group III were sacrificed 21 days after the operation. Every seventh slide of serial paraffin sections were stained with H&E stain, Red Holzer’s stain for glial fibers, Weigert’s and Van Gieson’s stain, Weil’s stain for myelin sheath, Peter’s protein silver stain for nerve fibers and Glee’s stain for degenerating nerve fibers . A close relationship between the processes of the pinealocytes and interstitial cells and capillaries was suggestive of an exchange of material between the two types of cells and blood vessels. Two types of acervulei in the control group, type I comprising of concentric whorl around a central heterochromatic nucleus and the type II made up of superimposed droplets were noted in the control group. Degenerating nerve fibers, cell free areas and acervulei of superimposed secretions were seen in group II and III suggesting an autonomic nervous control on the secretions of the gland.

Postnatal neurogenesis in the cow pineal gland: an immunohistochemical study.

Abstract: In the pineal gland of cows and rats structures designated rosettes have been described both during embryonic development and in adult animals. In order to investigate the possible nature of the cells comprising such structures, in the present work we studied the pineal glands from 10 cows of one- or four-years-old using conventional immunocytochemical and confocal microscopy techniques. As markers of glial cells, we used anti-vimentin (Vim) and glial fibrillary acidic protein (GFAP) and anti-S-100 sera, and the pinealocytes were labelled with s-III tubulin. As a marker of stem cells, we used an antinestin serum, while an anti-PCNA serum was employed to label proliferating cells. To explore the neuronal nature of some cells of the rosettes, we used an anti-SRIF serum. The rosettes were seen to be present throughout the glandular parenchyma and displayed a central cavity surrounded by cells, most of which expressed all or just some of the above glial labels and nestin, although there were also some rosettes with cells that expressed s-III tubulin and other cells that expressed SRIF. Likewise, in the cells of the rosettes the cell nucleus showed strong expression of PCNA. Confocal microscopy revealed that the walls of the rosettes contained cells that coexpressed Vim/S-100, Vim/GFAP and Vim/nestin. The number of rosettes was significantly greater in the animals of one year of age with respect to the four-year-old cows. The present findings allow us to suggest that rosettes are evolving structures and that most of the cells present in their walls should be considered stem cells, and hence responsible for the postnatal neurogenesis occurring in the pineal gland of cows.

Sustained adrenergic stimulation is required for the nuclear retention of TORC1 in male rat pinealocytes.

Abstract: The process involved in relocation of the coactivator, transducer of regulated cAMP-regulated element-binding protein (TORC) to the cytoplasm, unlike its activation, is not well understood. Using cultured pineal cells prepared from male rats, we found that although both α- and β-adrenergic stimulation could cause TORC1 dephosphorylation, only α-adrenergic stimulation was effective in the norepinephrine (NE)-mediated translocation of TORC1 into the nucleus. In contrast, blockade of either the α- or the β-adrenergic receptor after NE stimulation was effective in causing the rephosphorylation and rapid relocation of TORC1 into the cytoplasm. Studies with phosphoprotein phosphatase (PP) inhibitors indicated that although both PP2A and PP2B could dephosphorylate TORC1, only PP2B could cause translocation into the nucleus. However, after NE stimulation, treatment with either PP2A or PP2B inhibitors could cause the rephosphorylation and cytoplasmic relocation of TORC1. These results indicate a requirement of con...

Pineal gland: A structural and functional enigma

Abstract: The structures and functions of neuroendocrine pineal gland remains an enigma to both philosophers and scientists alike since time immemorial. Some of the structural and functional mysteries of pineal gland are unfolded to some extent in this article by reviewing the work of various researchers. Recently a neuronal circuit consisting of seven neurons between retina and pineal gland have been established to relate the effect of light and other rays on its secretion. The various physical properties such as piezoelectricity, piezoluminescence, electromagnetic field, solar flare, infrared energy are also explained and correlated with the structural and secretional components of the gland. The neurosecretion of pineal gland such as melatonin play an important role in sleep-wake patterns, timings and release of reproductive hormones along with temperature control. The presence of all enzymes needed for the synthesis of di-methyl-tryptamine (DMT) in pineal gland explains the near death experience (NDE) phenomenon. The various audio-visual hallucinations in NDE phenomenon occur due to massive increase of DMT in pineal gland before death. A very high concentration of di-methyl-tryptamine (DMT), presence of retinal proteins in 5–10% of pinealocytes, its role in thermoregulation and a possible role as magnetoreceptor in blind men and highest deposits of fluoride in the body are not only interesting but significant for the future research. Hence a lot of further research on pineal gland is still required to correlate its unique properties with its structural components.

Nucleolus-like bodies in the pineal gland of the adult yak ( Bos grunniens )

Abstract: The pineal glands of adult yak were studied electron microscopically. Nucleolus-like bodies (NLBs) were found mostly in the pinealocytes and the interstitial cells of the pineal glands of the yak. The NLBs were electron-dense, round or ovoid bodies with a diameter of 50 nm – 500 nm. Two types of granules were identified as melanin. These may correspond to different stages of a progressive storage of melanin. Rough endoplasmic reticula with abundant ribosomes were observed. There was no correlation between the number of NLBs and the sex of the animals.