Showing papers on "Pinealocyte published in 1979"
TL;DR: It is suggested that adenylate cyclase of pinealocytes is inactive during daytime, but is activated at night in darkness, which is transduced to the synthesis of N‐acetyltransferase molecules.
Abstract: —When pineal glands of 10–12-day-old chicks were organ-cultured in darkness, serotonin N-acetyltransferase activity was low during the daytime, increased at midnight and then decreased to the daytime level the next morning. The pattern of increase and decrease of enzyme activity in cultured pineal glands was comparable to the circadian rhythm of N-acetyltransferase activity in vivo. When pineal glands were kept at a low temperature for 5 h prior to culture, the phase of autonomous rhythm of enzyme activity was delayed. When chicken pineal glands were cultured during the daytime for 6 h, derivatives of adenosine 3′, 5′-monophosphate (cyclic AMP), cholera toxin, a high concentration of KCl and phosphodiesterase inhibitors increased N-acetyltransferase activity 3–7-fold, indicating an involvement of cyclic AMP in the regulation of N-acetyltransferase activity in chicken pineal gland as has been shown in rat pineal gland. When pineal glands were cultured at night in darkness, cholera toxin or a high KCl did not enhance the night-time increase of the enzyme activity. Derivatives of cyclic AMP or phosphodiesterase inhibitors enhanced the autonomous night-time increase of N-acetyltransferase activity in an additive or more than additive manner in cultured pineal glands. These observations suggest that adenylate cyclase of pinealocytes is inactive during daytime, but is activated at night in darkness, which is transduced to the synthesis of N-acetyltransferase molecules. Catecholamines suppressed the basal level and the nocturnal increase of N-acetyltransferase activity via α-adrenergic receptor. The nocturnal increase of enzyme activity was prevented by cycloheximide or actinomycin D. Cocaine, which stabilizes cell membrane potential or light exposure, blocked the nighttime increase of N-acetyltransferase activity in cultured chicken pineal glands.
124 citations
TL;DR: These experiments demonstrate the feasibility of using a neuropharmacologic approach to the mechanisms underlying mammalian circadian rhythms, and suggest that light and carbachol presumably act on the suprachiasmatic nucleus of the hypothalamus.
Abstract: Environmental lighting regulates numerous circadian rhythms, including the cycle in pineal serotonin N-acetyltransferase activity. Brief exposure of rats to light can shift the phase of this enzyme's circadian rhythm. Light also rapidly reduces nocturnal enzyme activity. Intraventricular injections of carbachol, a cholinergic agonist, can mimic both of these effects. Light and carbachol presumably act on the suprachiasmatic nucleus of the hypothalamus. These experiments demonstrate the feasibility of using a neuropharmacologic approach to the mechanisms underlying mammalian circadian rhythms.
118 citations
TL;DR: In the light of the different concepts treated, the confused state of comprehension of pineal functions becomes more understandable and most of the paradoxical and contradictory facts related to pineal function become less confusing.
Abstract: Publisher Summary In various recent reviews it has been concluded that the pineal body synthesizes a number of compounds and is an endocrine gland whose secretory products influence the development and function of the reproductive organs. It has been postulated that the pineal mediates certain environmental factors which regulate the function of the reproductive system. At present, no known pineal compound satisfies all of the classical criteria for a candidate hormone, that is, a substance produced exclusively in the pineal gland and having a specific functional influence on (a) distant target organ(s). In the light of the different concepts treated, the confused state of comprehension of pineal functions becomes more understandable. Only chemical identification of the different hormones synthesized in the pineal will permit the exact determination of pineal function. It is evident that one must think in terms of multiplicity of types of regulation in relation to the multiplicity of effects. Probably, the mammalian pineal gland is a synchronizer contributing to seasonal and probably also to circadian organization of functions. It is nonexclusively involved in different neuroendocrine mechanisms, which attunes the physiological adaptation of animals to their unique daily and annual patterns. When considering these points, most of the paradoxical and contradictory facts related to pineal function become less confusing.
108 citations
TL;DR: Experiments with glands from animals treated with 6-hydroxydopamine, with dispersed pinealocytes and with a number of relatively specific pre- and postsynaptic alpha-adrenergic agonists and antagonists have shown the receptors involved to be located at post Synaptic sites.
79 citations
TL;DR: The present findings indicate that nerve fibers from the habenular area actually terminate in the rat pineal gland.
Abstract: The neural connections of the pineal gland with the central nervous system (CNS) were studied in rats by stereotaxic lesioning followed by electron microscopic determination of nerve terminal degeneration. Electrolytic lesions were placed in the right medial habenular nucleus and after 3--14 days survival, the animals were prepared for electron microscopy. Control animals contained nerve terminals with 40--60 nm dense core vesicles located in the perivascular space of the pineal and in the intraparenchymal area. In the lesioned animals many electron-lucent degenerating nerve terminals could be observed intermingled with normal nerve terminals in the perivascular spaces. These degenerating terminals were often swollen and contained one side of the terminal. Both normal and degenerating nerve terminals were also observed in the parenchyma between the pinealocytes. The present findings indicate that nerve fibers from the habenular area actually terminate in the rat pineal gland.
74 citations
TL;DR: A diurnal rhythm in the cellular volume of gerbil pinealocytes was determined and it is suggested that, although part of the secretory product of the pinealocyte may be present in dense-cored vesicle, other locations could include the free cytoplasm and clear secretory vesicles.
Abstract: By means of morphometric analytical procedures, a diurnal rhythm in the cellular volume of gerbil pinealocytes was determined. This rhythm has been attributed primarily to a change in the cytoplasmic volume of the pinealocytes which is low during the daylight hours and increases to reach a peak during the middle of the dark period. At the ultrastructural level, six cytoplasmic components of the pinealocytes were found to exhibit a rhythm: free cytoplasm, smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER) and ribosomes, secretory vesicles, microtubules, and mitochondria. The presumptive secretory vesicles and the microtubules reached a peak in volume one hour before lights-off. It is suggested that lights-on and lights-off both signal a decrease in size and/or number of the secretory vesicles. The SER and RER/ribosomes reached their peak volume one hour after lights-off which is interpreted as indicating a peak in indoleamine synthesis and protein synthesis, respectively. The volume of free cytoplasm exhibits two peaks; one occurs one hour before lights-off while the second peak occurs in the middle of the dark phase. It is suggested that, although part of the secretory product of the pinealocyte may be present in dense-cored vesicles, other locations could include the free cytoplasm and clear secretory vesicles.
73 citations
TL;DR: This chapter highlights recent advances in pineal cytochemistry and also provides evidence of the production of indoleamines and proteinaceous substances by rudimentary photoreceptor cells and pinealocytes of amniota.
Abstract: Publisher Summary Pineal cells produce rhythmic signals and appear very responsive. In the pineal organ of Amniota, several types of messages may be elaborated: (1) in some reptiles, lacertilians and probably chelonians, the input of photic information may be converted into electrical signals, which are conducted to other parts of the brain; (2) in all groups of Amniota (reptiles, birds and mammals) chemical (neurohormonal) signals seem to be produced. Mainly from biochemical and physiological data it is concluded that two different categories of active pineal constituents (chemical signals) responsible for endocrine capabilities are elaborated; indoleamines now discovered in all Amniota and also low molecular weight compounds (possibly peptidic or polypeptidic), are found only in mammals. Other groups have not been investigated in this respect. However, at present, no pineal compound fully satisfies the classical criteria for a candidate hormone. This chapter highlights recent advances in pineal cytochemistry and also provides evidence of the production of indoleamines and proteinaceous substances by rudimentary photoreceptor cells and pinealocytes of amniota.
61 citations
TL;DR: In this paper, the pineal gland of the Mongolian gerbil following superior cervical ganglionectomy (SCGX) was studied and the effects of sympathetic denervation on the morphology of the gland at two time periods, 0500 and 1900 h (one hour before lights-on and lights-off, respectively).
Abstract: Morphometric analytical procedures were employed to study the pineal gland of the Mongolian gerbil following superior cervical ganglionectomy (SCGX). The purpose of this study was to define the effects of sympathetic denervation on the morphology of the gland at two time periods, 0500 and 1900 h (one hour before lights-on and lights-off, respectively). Fluorescence histochemistry was employed to determine catecholamine and indoleamine content in intact and denervated pineal glands. After SCGX, the pinealocytes decrease in size, concretions are prevented from forming, and the yellow fluorescence in the gland is lost. Following denervation a depression in the volume of most of the pinealocyte organelles, i.e., SER, RER/ribosomes, free cytoplasm, mitochondria and presumptive secretory vesicles, was also observed. However, synaptic ribbons increased in volume in the gerbils that had been killed at 1900 h. It appears that the sympathetic innervation to the pineal gland is a requirement for the presumptive secretory activity of the pinealocytes.
48 citations
TL;DR: The ability of pharmacologic p-agonists such as isoproterenol to produce an increase of N-acetyl transferase activity, and of &blockers such as propanolol to inhibit it, confirms that, in the rat, melatonin synthesis and presumably release, are mediated by a β -adrenergic system.
Abstract: Publisher Summary The mechanisms that control release of melatonin from the human pineal gland are unknown. This chapter mentions experimental data in animals which are relevant to the present study in humans. It has been established in animals, that the pineal gland is innervated by post-ganghonic fibers from the superior cervical ganglia, which secrete the neurotransmitter noreprinephrine. The presence of β -adrenergic receptors on pineal cell membranes has been demonstrated by the ability of β -adrenergic receptor antagonists to competitively inhibit norepinephrine-induced actions in pinealocyte metabolism. Among the more important of these actions are the activation of adenyl cyclase and the induction of N-acetyl transferase activity, resulting eventually in increased melatonin synthesis. The ability of pharmacologic p-agonists such as isoproterenol to produce an increase of N-acetyl transferase activity, and of &blockers such as propanolol to inhibit it, confirms that, in the rat, melatonin synthesis and presumably release, are mediated by a β -adrenergic system. Further, the sensitivity of these receptors to stimulation appears to vary inversely with the extent of previous stimulation. In addition to a β -adrenergic system, there is some evidence of a dopaminergic influence on melatonin synthesis, as dopamine increases melatonin production in organ culture. In addition, L-dopa increases rat pineal melatonin concentration and N-acetyl transferase activity.
46 citations
TL;DR: It is suggested that the vesicles of RF may arise from those of the SER and that MF may play a role in the movement of SER-vesicles to those areas of the cytoplasm where new RF are being formed.
Abstract: Microfilaments (MF, 5-8 nm in diameter) are a prominent feature of the pinealocyte cytoplasm of baboons (Papio ursinus) kept under controlled lighting conditions. MF occurred as a filamentous network in these cells during the light phase of the diurnal light-dark cycle, while a close structural association was noted between MF and the membranes of the smooth endoplasmic reticulum (SER). This association was especially evident during the dark period. Increased numbers of single synaptic ribbons (SR, vesicle-crowned rodlets), together with large aggregations of SR, i.e., ribbon fields (RF), were seen in the pinealocyte cytoplasm of baboons killed during the dark phase. It is suggested that the vesicles of RF may arise from those of the SER and that MF may play a role in the movement of SER-vesicles to those areas of the cytoplasm where new RF are being formed.
45 citations
TL;DR: Using proteases and the PA-TCH-silver technique on ultrathin sections, it was concluded that the dense core of DCV was proteinaceous in nature.
Abstract: Electron dense-cored vesicles (DCV), originating in the Golgi apparatus and migrating into the perivascular processes, constitute a characteristic feature of the pinealocytes in the pineal gland of mice and hamsters. This report presents the results of ultracytochemical studies carried out to clarify the nature and physiological significance of these vesicles. Using proteases and the PA-TCH-silver technique on ultrathin sections, it was concluded that the dense core of DCV was proteinaceous in nature. These data, correlated with previous pharmacological and cytophysiological studies, showed the important role of DCV in the storage and intracellular migration of a proteinaceous compound of unknown significance. However, in agreement with authors who hypothesized the elaboration of active peptidergic compounds in the mammalian pineal gland to explain some effects that could not be ascribed to indoleamines, it was proposed that DCV might store a carrier-neurohormone complex. The presence in the DCV of one indoleamine, such as serotonin, or of several indoleamines, has still not been established in mammals.
TL;DR: This chapter describes the pinealocyte as aParaneuron and proves the usefulness of the paraneuron concept for answering questions in pineal research.
Abstract: Publisher Summary This chapter describes the pinealocyte as a paraneuron and proves the usefulness of the paraneuron concept for answering questions in pineal research Main representatives of the paraneuron family are, for example, (a) peptidergic hormoneproducing endocrine cells like the chromaffin cells of the adrenal medulla, parafollicular cells of the thyroid, parathyroid cells, anterior pituitary cells, pancreatic islet cells, and basal granular cells in the gastro-intestinal tract, (b) sensory cells like the gustatory cells, hair cells of the inner ear and the lateral line organs, olfactory cells, photoreceptor cells of the retina, the pinealocytes, and liquorcontacting neurons, and (c) Merkel cells of the skin, melanocytes, and mast cells All criteria characteristic of a paraneuron hold for the pinealocyte, but the same criteria are also properties of nerve cells Naturally, there is no clear boundary between a neuron and a paraneuron The distinction between a receptive region and an output region in paraneurons may help to explain morphological findings related to the location of end-feet of pinealocytes at the region of the basal lamina Distinguishing between a receptive input, a conductive, and an output region in paraneurons may be useful in obtaining more information about this enigmatic cell organelle in mammalian pinealocytes
TL;DR: During development, the synaptic ribbons increase in length, and dense core vesicles are frequently found in the vicinity of these structures, which are considered to be engaged in a certain form of secretory activity of the mammalian pineal gland.
Abstract: Synaptic ribbons, functionally enigmatic structures of mammalian pinealocytes, were studied during the postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus). On day 4 post partum, synaptic ribbons appear in cells that have already started to differentiate into pinealocytes. Between days 4 and 9, an increase in the number of synaptic ribbons occurs, concomitant with the continuing differentiation of the pineal tissue. Between days 9 and 16, when differentiation of this tissue is almost completed, the number of synaptic ribbons decreases and approaches that characteristic of the adult pineal gland. During development, the synaptic ribbons increase in length, and dense core vesicles are frequently found in the vicinity of these structures. It is assumed that a functional relationship exists between dense core vesicles and the synaptic ribbons, which are considered to be engaged in a certain form of secretory activity of the mammalian pineal gland.
TL;DR: Dense cored vesicles in the pinealocytes and small granulated vesicle in the nerve fibers of the hamster pineal gland contain 5-HT, and the population of dense bodies in the Pinealocytes is heterogenous, some are lysosomes and the others are possibly the granules responsible for the secretion of pineal peptides.
Abstract: The pineal gland of adult golden hamsters (Mesocricetus auratus) was studied by various cytochemical methods at the electron microscopic level: (1) the modified chromaffin reaction specific for 5-hydroxytryptamine (5-HT), (2) argentaffin reaction, (3) zinc-iodide-osmium (ZIO) mixture reaction and (4) acid phosphatase reaction. In the pinealocytes, the dense-cored vesicles (80–160 nm in diameter) show both chromaffinity and argentaffinity, while the population of dense bodies (150–400 nm in diameter) is reactive to ammoniacal silver solution and ZIO mixture but not to the modified chromaffin reaction. After incubation for demonstration of acid phosphatase activity, reaction products are localized in some, but not all, of the dense bodies, in some of the small vesicles in the Golgi region and in one or two inner Golgi saccules. In nerve fibers in the pineal gland, small granulated vesicles are also reactive to the modified chromaffin reaction and ZIO mixture. Based upon these cytochemical results the following conclusions have been reached: (1) dense cored vesicles in the pinealocytes and small granulated vesicles in the nerve fibers of the hamster pineal gland contain 5-HT, and (2) the population of dense bodies in the pinealocytes is heterogenous, some are lysosomes and the others are possibly the granules responsible for the secretion of pineal peptides.
TL;DR: The perikaryonal cytoplasm of pinealocytes is characterized by the presence of inclusion bodies, usually round in shape, not bounded by a limiting membrane and composed of fine granular or filamentous materials of high electron-opacity, which are similar in appearance to the substance seen in the nucleolonema.
Abstract: Fine structural features of pinealocytes of cotton rats (Sigmodon hispidus) were examined. Golgi complexes, mitochondria, endoplasmic reticulum and polysomes are usual organelles seen in the perikaryonal cytoplasm of pinealocytes. Many non-granulated vesicles (40 to 80 nm in diameter) and a few granulated vesicles (about 100 nm in diameter) are associated with the Golgi cisternae. Occasionally, the cisternae contain granular materials. The perikaryonal cytoplasm of pinealocytes is characterized by the presence of inclusion bodies. These bodies are usually round in shape, not bounded by a limiting membrane and composed of fine granular or filamentous materials of high electron-opacity, which are similar in appearance to the substance seen in the nucleolonema. Pinealocyte processes, filled with abundant non-granulated vesicles and some granulated vesicles, are mainly found within the parenchyma and occasionally in perivascular spaces.
Journal Article•
TL;DR: It is concluded that the number of granular vesicles in mouse pinealocytes (and in their Golgi regions) follows a 24 hour rhythm, and that the nocturnal decrease in the vesicle number depends upon darkness.
Abstract: Adult (70-100 days) male dd-mice were killed at 7 a.m., 1 p.m., 7 p.m. and 1 a.m. under controlled daily photoperiods (L: 7 a.m.-7 p.m.) and temperature, and at 6, 12 and 18 hours after exposure to continuous lighting which started at 7 p.m. Montage photographs were made from electron micrographs at x8200 based on mesh hole areas, using either 150 or 300 meshes. The number of granular vesicles per unit area was counted (GV Score). The GV Score in distal, mid and proximal portions of the body of the pineal gland showed marked 24 hour change, with high values in the late light period and low values in the dark period. The GV Score in the Golgi region showed a 24 hour change with a smaller amplitude. A peak level was attained at mid-light period and low values during a dark period. Additional lighting inhibited the nocturnal decrease in the GV Score in both the whole cytoplasm and the Golgi region, resulting in a slight increase. It is concluded that the number of granular vesicles in mouse pinealocytes (and in their Golgi regions) follows a 24 hour rhythm, and that the nocturnal decrease in the vesicle number depends upon darkness.
TL;DR: The circadian rhythm of melatonin synthesis in the pineal glands of various species has been summarized and the avian pineal gland may play a biological clock function to control the circadian rhythms in physiological, endocrinological and biochemical processes via pineal hormone melatonin.
Abstract: The circadian rhythm of melatonin synthesis in the pineal glands of various species has been summarized. The night-time elevation of melatonin content is in most if not all cases regulated by the change of N-acetyltransferase activity. In mammals, the N-acetyltransferase rhythm is controlled by the central nervous system, presumably by suprachiasmatic nuclei in hypothalamus through the superior cervical ganglion. In birds, the circadian oscillator that regulates the N-acetyltransferase rhythm is located in the pineal glands. The avian pineal gland may play a biological clock function to control the circadian rhythms in physiological, endocrinological and biochemical processes via pineal hormone melatonin.
TL;DR: This chapter checks if neurophysiological properties of pinealocytes can be related to circadian changes in melatonin synthesis in guinea-pig pineal organ.
Abstract: Publisher Summary Recent electrophysiological studies have shown that the guinea-pig pineal organ comprises two main categories of intrinsic cells, which are (a) pinealocytes which are predominantly influenced by central commissural fibers and (b) pinealocytes which are exclusively influenced by peripheral sympathetic fibers. The first group comprises spontaneously active cells which respond to olfactory, acoustic and short-term optic stimuli respectively. After sympathectomy their spontaneous activity is diminished but not suppressed. The second group comprises spontaneously active cells, which do not respond to short-term sensory stimulation and whose activity depends on the environmental lighting conditions. After sympathectomy, these cells cease firing. This chapter checks if neurophysiological properties of these cells can be related to circadian changes in melatonin synthesis.
TL;DR: A mammalian fetal nerve is suggested to be ontogenetically equivalent to the pineal nerve (nervus pinealis) present in anuran amphibians, which can be related phylogenetically to a possible homologous structure present in lower vertebrates.
Abstract: Publisher Summary The epiphysis cerebri of lower vertebrates (cyclostomes, fishes, amphibians and reptiles) is a structure with a sensory function containing cone-like photoreceptor cells. A pineal nerve (nervus pinealis), penetrating the skull, connects the frontal organ and the intracranially situated epiphysis cerebri. The nerve fibers continue in a caudal direction as the pineal tract, located in the wall of the intracranial epiphysis, then entering the brain and reaching the region of the posterior commissure. During phylogenetic development, this photoreceptive organ becomes a secretory organ. However, in birds rudimentary photoreceptive cells are still present, but in the adult mammals the pinealocytes are exclusively secretory cells. During ontogenesis histological and cellular changes indicate a similar development from photoreceptive cell to secretory cell. In neonatal rat and hamster pineals, cellular projections containing membranes showing a lamellate and vesicular organization resembling the outer segments of primitive cones are -observed. Studies in author's laboratory on fetuses from humans, sheep and rabbit revealed a structure, present during ontogenesis, which can be related phylogenetically to a possible homologous structure present in lower vertebrates. This mammalian fetal nerve is suggested to be ontogenetically equivalent to the pineal nerve (nervus pinealis) present in anuran amphibians. The function of the nerve in the differentiation of the mammalian pineal gland is, at present, purely speculative.
TL;DR: It is concluded that norepinephrine stimulates [ 14 C]taurine release from pinealocytes by acting through a cyclic AMP mechanism.
TL;DR: The increased incidence of synaptic ribbons in pinealocytes which appear to be in a heightened state of activity strongly suggests a function for this structure and lends credence to the possibility that this structure may serve a sensory or receptor function in the guinea pig gland.
Abstract: Pinealocyte ultrastructure has been studied in four sterile, four pregnant and three fertile but non-pregnant females, and also in three reproductively active male pigmented Duncan Hartley guinea pigs. Synaptic ribbons are dense, rod-like structures with a linear arrangement of clear vesicles periodically spaced on both sides of the rodlet. Although these structures were observed in the pinealocytes of all of the animals studied, they were scarce and difficult to locate in tissue from the fertile, non-pregnant females and from the reproductively active males. They were numerous in the pineal glands of the pregnant and sterile females. Typically they lie perpendicular to the cell membrane of the pinealocyte polar process and in close proximity to a polar process of a neighboring cell. The increased incidence of synaptic ribbons in pinealocytes which appear to be in a heightened state of activity strongly suggests a function for this structure. Synaptic ribbons are also present in sensory systems such as rods and cones of the retina, hair cells of the organ of Corti and hair cells of the vestibular apparatus. This fact, plus the photoreceptor function of pinealocytes in lower vertebrates, lends credence to the possibility that this structure may serve a sensory or receptor function in the guinea pig gland.
TL;DR: The pinealocytes of the pig contain a large number of aldehydefuchsin positive granules, and their morphological appearance strongly suggests that they belong to the lysosomal system.
Abstract: The pinealocytes of the pig contain a large number of aldehydefuchsin positive granules In order to determine their nature an ultrastructural study was carried out Numerous bodies having a maximal diameter of about 1,600 nm were found These elements showed a great variety of internal structure, ranging from a “homogeneous” content and amorphous dense aggregates to lamellate bodies Although only a few of them displayed a positive reaction for acid phosphatase, their morphological appearance strongly suggests that they belong to the lysosomal system
TL;DR: It is concluded that succinate dehydrogenase activity in the pineal gland of the rat is regulated by changing the concentration of the active enzyme itself as well as the level of the endogenous coenzyme Q.
Abstract: Succinate dehydrogenase activity was investigated histochemically in the rat pineal gland. The influence of fixation on the activity pattern, the possible diffusion of enzyme, the nothing dehydrogenase reaction, and the substantivity of the tetrazolium salts and formazans were investigated in control experiments. In rats maintained on a 17/7 h light/dark schedule a distinct circadian rhythm of the succinate dehydrogenase was demonstrated in the pineal gland. Activity was lowest during the day and highest during the night. The dorsocaudal part of the gland showed the highest activity and within the same part of the gland the activity varied between individual pinealocytes. A relative lack of endogenous coenzyme Q, as well as a circadian rhythm of this coenzyme, highly influenced the activity of succinate dehydrogenase. It is concluded that succinate dehydrogenase activity in the pineal gland of the rat is regulated by changing the concentration of the active enzyme itself as well as the level of the endogenous coenzyme Q. Whether this is caused by a circadian rhythm in the synthesis or in the catabolism of the enzyme and the coenzyme was not revealed by the present study .
TL;DR: The results of this study do not support the previous theory that melatonin plays an important role in the regulation of the pinealocytes secretory process, but instead points more directly to the significant role that norepinephrine has in controlling pinealocyte secretion.
Abstract: The number of granulated vesicles in mouse pinealocytes exhibit a distinct circadian rhythm which is abolished by superior cervical ganglionectomy. Since melatonin treatment markedly affects the number of pinealocytic granulated vesicles, it was suggested that a relationship may exist between norepinephrine, melatonin, and the synthesis and/or secretion of pinealocyte granulated vesicles. The present study was undertaken in an attempt to clarify this relationship. Mice were housed in an environmental chamber under controlled lighting (12L/12D), and were treated with either reserpine, a drug which depletes serotonin and norepinephrine, or p-chlorophenylalanine (p-CPA), an inhibitor of serotonin synthesis. They were sacrificed at various times over a twenty-four hour period, and granulated vesicles present in the pinealocytes were quantitated in thin cross sections through pericapillary areas. Reserpine treatment resulted in a marked increase in the number of granulated vesicles during the dark, but led to a slight decrease during the photoperiod. Treatment with p-CPA produced no significant effect. The results of this study do not support our previous theory that melatonin plays an important role in the regulation of the pinealocyte secretory process, but instead points more directly to the significant role that norepinephrine has in controlling pinealocyte secretion.
TL;DR: The results suggest that SCG is a target tissue for oestrogens, and oestradiol treatment counteracted the depression in tubulin levels of decentralized SCG.
TL;DR: The preliminary results show that in the pineal organ of fishes under certain circumstances, ultrastructural elements can be found which might indicate the presence of secretory products.
Abstract: Publisher Summary Based on ultrastructural investigations of the pineal organ of several teleost fish species, some morphological features are presented which might be relevant to the supposed endocrine activity of the pineal organ of fishes. In the rudimentary photoreceptor cells of reptiles and in the pinealocytes of birds and mammals, large dense-core vesicles are a common phenomenon. They are regarded as secretory granules that might contain indoleamines or proteins or both. Another morphological feature which might be related to a secretory activity of the pineal organ is the presence of electron-dense material in the intercellular spaces. This intercellular material has been observed frequently in the pineal organ of all the fish species that were studied, for example Hyphessobrycon scholzei , Hemmigrammus caudovittatus , Astyanax mexicanus , Hippocampus hudsonius and Nannostomus beckfordi . The origin of the material is not known, but the presence of similar electron-dense material in vesicles and in finger-like structures in the supporting cells suggests that this material can be taken up from or released into the intercellular spaces by the pineal supporting cells. A third morphological feature that might be connected with the supposed endocrine activity is the occurrence of lipid inclusions in the pineal organ of all the species of fish that were studied in this investigation. The preliminary results show that in the pineal organ of fishes under certain circumstances, ultrastructural elements can be found which might indicate the presence of secretory products.
TL;DR: The acid phosphatase reaction was studied in the chicken pineal gland from the moment of hatching until 2 months of age and the dense polymorphous bodies of the B pinealocytes are ultrastructurally identified as lysosomes.
Abstract: The acid phosphatase reaction, applied to light and electron microscopy, was studied in the chicken pineal gland from the moment of hatching until 2 months of age. From the moment of hatching there is a great amount of acid phosphatase, which is mainly found in the vicinity of the lumen of both the recess and large follicles. Acid phosphatase is poor in the parafollicular layer. From day 30 onwards, there is an obvious fragmentation of the recess and of large follicles. Also, the parafollicular layer differentiates to form new follicles. The dense polymorphous bodies of the B pinealocytes are ultrastructurally identified as lysosomes.
TL;DR: This study indicates that the pineal of mink only contains one single population of pinealocytes, and there is evidence of a blood-brain barrier within the mink pineal gland.
Abstract: The pineal gland of normal and experimental female mink has been studied by light-, fluorescence- and electron microscopy. The general structure of the mink pineal is described. Two main cell types are recognized. One, termed pinealocyte, predominates in number. Though slight morphological differences (e.g. electron density of the cytoplasm and content of organelles) were observed, this study indicates that the pineal of mink only contains one single population of pinealocytes. The other, termed glial cell, inserted between the pinealocytes, is characterized by the presence of elongated processes, containing microfilaments. Different treatments (ovariectomy and LH—RH administration) and different endocrine states during the year induced morphological changes in the pinealocytes. A rich network of nerve fibres containing electron-dense granules (40–50 nm) is observed. Microspectrofluorometrically these fibres exhibit the spectral characteristics of cateholamines. All the pinealocytes show a yellow fluorescence. This cellular fluorophor shows the same microspectrofluorometric characteristics as does the fluorophor of serotonin. Occasionally, synaptic ribbons are observed in the perikaryon and the processes of the pinealocytes. A large number of cellular junctions between pinealocytes and endothelial cells is present. Their presumed function(s) are discussed. There is evidence of a blood-brain barrier within the mink pineal gland.
TL;DR: The results described here partially agree with the studies on Spalax ehrenbergi Nehring in favor of a multihormonal function of the pineal gland, in agreement with the opinion of some other authors.
Abstract: Publisher Summary This chapter focuses on different populations of pinealocytes in the pineal gland of the mole-rat (Spalax leucodon, Nordmann). The ultrastructural characteristics of the cells, combined with light-microscopic findings, suggest the existence of different populations of pinealocytes. The accumulations of granular endoplasmic reticulum and mitochondria in some cells, the abundance of large vacuoles and cisternae of endoplasmic reticulum in others, the presence of crystalloid contents within the perinuclear space in a third type of cells, and the presence of pinealocytes with large granules in a fourth, all particular cytologic characteristics in the process of protein synthesis, speak in favor of the presence of cells with different physiological characteristics. The cells containing accumulations of lipid droplets can be identified with those which were characterized by the presence of PAS-positive granules. This would indicate the presence of a glycolipid product in a certain type of pinealocytes. The results described here partially agree with the studies on Spalax ehrenbergi Nehring . They are in favor of a multihormonal function of the pineal gland, in agreement with the opinion of some other authors.
TL;DR: It appears that pineal richness in metabolic active monoamines runs parallel with sexual hypoactivity and that different ultrastructural aspects of the pinealocyte correspond to distinct ovarian activity, which appears before the corresponding ovarian state.
Abstract: Publisher Summary The relationships between the epiphysis and the gonadal axis that have been extensively surveyed may appear more clearly during particular physiological states. Therefore, it seems interesting to study the gland in a hibernant animal, the garden-dormouse, which has a seasonal sexual cycle and is very sensitive to photoperiod variations. Hibernating and animals in the dark are in complete anoestrus, whereas in continuously lightened animals a progressive sexual activation is observed. It appears that pineal richness in metabolic active monoamines runs parallel with sexual hypoactivity and that different ultrastructural aspects of the pinealocyte correspond to distinct ovarian activity. These aspects appear before the corresponding ovarian state. Hypothalamic catecholamines were studied in the same series of animals. This chapter shows that, when the pineal monoaminergic metabolism is quiescent (illumination), hypothalamic catecholamines are very active, luteinizing hormone-releasing hormone (LHRH) is synthesized and released, while genital activation occurs. When the pineal monoaminergic metabolism is strong (hibernating and animals kept in the dark), hypothalamic catecholamines and LHRH show low activity, while the animals are sexually hypoactive.