Twenty-four-hour changes in pinealocytes,capillary endothelial cells and pericapillary and intercellular spaces in the pineal gland of the mouse

Summary Semiquantitative electron-microscopic observations on the pineal gland of dd-mice were carried out to determine whether 24-h rhythms exist in pinealocytes, pericapillary and intercellular spaces and capillary endothelial cells. Nuclear and cytoplasmic areas of pinealocytes and the area of condensed chromatin in pinealocytes showed inversely related circadian rhythms; the former two increased, whereas the latter decreased, during the light period. The extent of pericapillary and wide intercellular spaces exhibited 24-h changes, with an increase and decrease occurring during the light period and the dark period, respectively. The cross-sectional area of endothelial cells decreased and the number of fenestrae increased during the light period; this was reversed during the dark period. The results suggest that the increase in the nuclear and cytoplasmic areas of pinealocytes, the area of pericapillary and wide intercellular spaces and the number of fenestrae, and the decrease in the area of condensed chromatin and endothelial cells during the light period may be related to an increase in synthetic activity of pinealocytes in the mouse.     

Expression of neuron-specific enolase in the pineal organ of the domestic fowl during post-hatching development

Immunohistochemistry for neuron-specific enolase (NSE) revealed that NSE is localized in both a limited number of pinealocytes and intrinsic afferent neurons in the pineal organ of the domestic fowl. Furthermore, a computer-assisted three-dimensional imaging technique allowed to clarify the reverse distributional pattern of both elements: NSE-positive pinealocytes displayed a dense distribution especially in the vesicular portion of the gland, whereas NSE-immunoreactive nerve cells were mainly found in the pineal stalk. The number of NSE-positive intrinsic neurons in the pineal organ of chickens decreased rapidly after hatching, with a concentration of these elements in the basal portion (stalk) of the pineal organ. On the other hand, immunoreactive pinealocytes increased remarkably in the end-vesicle of the organ with age, followed by a gradual expansion toward the proximal portion. Thus, the spectacular increase in NSE-positive pinealocytes and the progressive reduction of reactive neurons occurred in parallel during the course of post-hatching development. NSE-immunoreactive pinealocytes displayed morphological characteristics of bipolar elements, endowed with an apical protrusion into the pineal lumen and a short basal process at younger stages, whereas multipolar types of NSE-positive pinealocytes were predominantly found in the adult domestic fowl. These results indicate that in the pineal organ of the domestic fowl (1) the ontogenetic expansion of NSE-immunoreactive pinealocytes is paralleled by a regressive afferent innervation, (2) the NSE-positive pinealocytes transform from a bipolar (columnar) type to a multipolar type during post-hatching development, and (3) these ontogenetic changes in the NSE-immunoreactivity and morphology of pinealocytes may reflect the development of a neurosecretory-like capacity of the organ.     

The Pineal Gland of the Mink, Mustela vison: Light-, Fluorescence- and Electron Microscopical Studies

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.     

The influence of some sympatholytic,parasympatholytic and serotonin-synthesis-inhibiting agents on the ultrastructure of the rabbit pineal organ

The influence of certain drugs on the ultrastructure of rabbit pinealocytes was studied. The results obtained after administration of p-chlorophenylalanine and p-chloroamphetamine support the hypothesis proposed earlier that the smooth endoplasmic reticulum in the light pinealocytes is involved in indoleamine synthesis. The administration of either one of the sympatholytic agents, 6-hydroxydopamine or alpha-methyl-p-tyrosine, induced typical fine structural changes corresponding to those observed after surgical sympathectomy.     

The pineal gland of the gerbil,Meriones unguiculatus

Summary Electron microscopy was employed in a study of the pineal gland of the Mongolian gerbil (Meriones unguiculatus). It was determined that the gerbil pineal gland contains pinealocytes and glial cells with the pinealocytes being the predominant cell type. The pinealocytes contain numerous organelles traditionally considered as being either synthetic or secretory in function such as an extensive Golgi region, smooth (SER) and rough (RER) endoplasmic reticulum, secretory vesicles and microtubules. Other cytoplasmic components are also present in the pinealocytes (synaptic ribbons, subsurface cisternae) for which no function has been assigned. Dense-cored vesicles are rare. Vacuolated pinealocytes are present and appear to be intimately associated with the formation of the pineal concertions. Evidence presented supports the proposal that the concretions form within the vacuoles. Once the concretions reach an enlarged state, the vacuolated pinealocytes break down and the concretions are thus extruded into the extracellular space where they apparently continue to increase in size. The morphology of the glial cells was interpreted as indicative of a high synthetic activity. The glial cells contain predominantly the rough variety of endoplasmic reticulum and form an expansion around the wide perivascular area.Supported by NSF grant PCM 77-05734     

The effects of melatonin, N-acetylserotonin, and 6-hydroxymelatonin on the ultrastructure of the pinealocytes of the Syrian hamster (Mesocricetus auratus)

OBJECTIVES: The aim of this study was to examine the effects of melatonin as well as of its precursor (N-acetylserotonin) and metabolite (6-hydroxymelatonin) on the ultrastructure of the pinealocytes of the Syrian hamster. MATERIAL AND METHODS: The pineal glands of 2-month-old male Syrian hamsters were examined. The animals were divided into the following groups of four animals each: group 1 - melatonin treatment; group 2 - N-acetylserotonin treatment; group 3 - 6-hydroxymelatonin treatment (all substances given subcutaneously at doses of 25 microg per animal between 16.00 and 17.00 h daily for seven weeks). Group 4 was given solvent treatment only and served as controls. The animals were killed by decapitation between 09:00 and 10.00 h. Routine electron microscopical techniques were used to obtain quantitative data on pinealocyte ultrastructure. RESULTS: Melatonin administration did not influence the size of the hamster pinealocytes, whereas administration of N-acetylserotonin and 6-hydroxymelatonin caused a significant reduction in cell size in comparison to the melatonin-treated and control groups. There were changes in the relative volumes of the mitochondria, Golgi apparatus and lysosomes in the pinealocytes of the studied groups, while the volumes of granular endoplasmic reticulum and lipid droplets were unchanged. The dense-core vesicles were more numerous in the pinealocytes of the melatonin and 6-hydroxymelatonin-treated groups in comparison to those of animals treated with N-acetylserotonin or the controls. CONCLUSIONS: The changes observed in the ultrastructure of hamster pinealocytes indicate that administration of melatonin as well as of its precursor or metabolite influences the morphology of these cells and also, perhaps, their secretory activity.     

Influence of gonadotropic hormones on the ultrastructure of rat pinealocytes

Summary The influence of gonadotropic hormones on the ultrastructure of rat pinealocytes was studied. Human chorionic gonadotropin (HCG) as well as pregnant mare serum gonadotropin (PMSG) caused a marked activation of pinealocytes. It is characterised by a conspicuous proliferation of the granular endoplasmic reticulum and Golgi apparatus as well as an increase in number of dense core vesicles, mitochondria, dense bodies, subsurface cisternae and vesicles in the terminal buds of pinealocyte processes. The changes after HCG administration were more pronounced than after PMSG.Supported by a grant from the Polish Academy of Sciences, No. 10.4.2.01.5.6     

Postnatal maturation of the parenchymal cell types in the rabbit pineal gland.

An ultrastructural study on the maturation of the parenchymal rabbit pineal cell types from the first postnatal day up to 120 days is presented. Two main cell types are distinguished from the first 24h of postnatal life. Pinealocytes of the types I and II display different developmental degrees. Both immature cell types are arranged in groups. In addition, type II pinealocytes form rosette-like structures. Both cell types progressively become isolated and display cell processes. The nucleus and the cytoplasm of type I pinealocytes are barely electrondense. During the postnatal period, the number of cytoplasmic organelles, cell processes and terminal clubs increase progressively. Terminal clubs are frequently seen near blood vessels. After 30 days, type I pinealocytes show characteristics of adult pinealocytes. However, the maturation of most type I pinealocytes does not complete until the 90th postnatal day. Type II pinealocytes present a fairly electrondense nucleus and cytoplasm. Mature forms can be seen after the 5th postnatal day. During the postnatal period, a close relationship is determined among type II pinealocytes and cell processes and terminal clubs of type I pinealocytes.     

Effects of Hypoxia,Hyperbaria and Hyposmosis on Ecto- ATPase Activity in Scorpionfish (<Emphasis Type="Italic">Scorpaena porcus</Emphasis> L.) Erythrocytes

Effects of hypoxic, hyperbaric and hyposmotic exposures on activity of erythrocyte membrane-bound ecto-ATPase were studied in the scorpionfish Scorpaena porcus L. One-hour autogenic hypoxia evoked a drop while longer hypoxia (12, 24 h)–a rise in the enzyme activity. Hyperbaric exposure, irrespective of its duration, evoked the same stimulation of ecto-ATPase activity in vivo. In vitro, instead, hydrostatic pressure caused a significant drop in the enzyme activity. Hyposmosis stimulated ecto-ATPase activity when the medium was diluted to 50% of its basal level, however, a stronger dilution (70%) led to its inhibition. Under hypoxia, changes in ecto-ATPase activity of scorpionfish erythrocytes are, most likely, due to a shift in the hormonal background and the plasma acid–base equilibrium. The reasons behind the activation of erythrocyte ecto-ATPase in response to hyperbaric pressure are obscure. Under in vitro conditions, the direct effect of hyperbaria and hyposmosis on scorpionfish erythrocytes may be due to alterations in characteristics of plasma membrane microviscosity and in the ecto-ATPase conformational state as manifested in fluctuations of enzyme activity during experiments.     

The influence of acute hypoxia on the functional and morphological state of the black scorpionfish red blood cells

The investigation of the mechanisms of red blood cell steadiness to the oxygen lack in tolerant teleosts is of current scientific interest. Black scorpionfish, Scorpaena porcus L., is a widespread benthal species in the Black Sea and is highly resistant to hypoxic influence. The morphological state of black scorpionfish red blood cells under acute hypoxia was assessed using DNA-binding dye SYBR Green I and fluorescent microscopy. Changes in membrane potential of mitochondria and functional activity of cells were determined by rhodamine 123 (R123) and fluorescein diacetate (FDA) fluorescence. Oxygen deficiency leads to bidirectional changes in volume of erythrocytes and their nuclei. Between 0.57 and 1.76 mg О₂ l^?1, both parameters increased on 3–12 and 7–21%, respectively. At 1.76–4.03, cells shrank on 1.5–6.0% and nucleus size decreased on 1.5–3%. Acute hypoxia induced a significant increase of R123 (12–60%) and FDA (30–184%) fluorescence. These reactions are caused by a probable decrease in erythrocyte membrane permeability.     

Age-related morphometric changes in the pineal gland. A comparative study between C57BL/6J and CBA mice

Relatively little is known about the effects of melatonin on the aging of the pineal, the organ which is the main place for synthesis of this hormone. Using simple morphometric methods, some parameters of the pineal gland, such as total volume, number of pinealocytes and pinealocyte volume were estimated in two mice strains: normal CBA and melatonin-deficient C57BL/6J. Two age groups, 6 weeks and 10 months, were studied in order to evaluate possible differential age-related changes between both strains. Pineals of both strains have similar morphometric and morphological features at 6 weeks of age. This suggests that pineal development, which has already concluded at 6 weeks of age, is not affected by the absence of melatonin synthesis in the pinealocytes. Later on, CBA pineal showed an increase in size caused by cellular hypertrophy. In contrast, the C57BL/6J pineal volume decreased by loss of pinealocytes in the same period of time. Semithin sections analysed by light microscopy did not show that this cell death was evident in the C57BL/6J strain at any of the ages studied. Thus, a gradual loss of pinealocytes could be hypothesised in these pineals. These results suggest that pineal melatonin could have a role in the maintenance of pinealocyte viability and the increase of pineal size which takes place after development. The abnormal pattern observed in the C57BL/6J pineal should be taken into account in future studies on this gland.     

Male mating effort in the viviparous scorpionfish,Sebastiscus marmoratus

Males of some internally fertilizing fishes devote reproductive efforts not only to mating activities but also to sperm production. Male reproductive efforts of the viviparous scorpionfish,Sebastiscus marmoratus, an ambush predator usually remaining on the substrate, were studied at a rocky coast in southern Japan. During the mating season in early winter, males actively visited and courted several females, and interacted aggressively with other males. Females remained stationary. Seasonal changes in somatic and gonad weights suggested that males devote reproductive efforts to such mating activities, rather than to sperm production. Because females almost always ignored frequent courtships from several males, resulting in infrequent copulations, and would rarely copulate with multiple males, sperm competition is not likely to be intensive. Accordingly, males may increase mating efforts while retaining small testis size (max. GSI=0.4%), smaller than that in many externally fertilizing fishes. The reproductive effort of this species is compared with that of other viviparous fishes.     

Influence of 4-day long treatment with vasoactive intestinal peptide on ultrastructure and function of the rat pinealocytes in organ culture

Vasoactive intestinal peptide (VIP) is one of neuropeptides involved in the regulation of the pineal gland function. The acute treatment of rat pinealocytes with VIP caused changes in their biochemical parameters. The present study concerns the effects of the chronic treatment with VIP on ultrastructure and function of the rat pinealocytes in organ culture. The pineals of adult male rats were assigned to one of three groups and placed in organ culture for four consecutive days. The pineals of the first group were incubated in the control medium, the pineals of the second group--12 hrs in control medium and 12 hrs in medium with 1 microM VIP (between 20.00 and 8.00) during each day, the pineals of the third group--24 hrs per day in medium with 1 microM VIP. The melatonin concentration was measured using RIA and activity of enzymes using radiochemical methods. Point count method was used in quantitative ultrastructural analysis. Both modes of chronic treatment with VIP increased significantly the level of melatonin secretion during four days of the culture and the content of this hormone in the pineal explants at the end of the experiment. Treatment with the neuropeptide for 12 hrs and 24 hrs per day elevated also the activity of arylalkylamine N-acetyltransferase and hydroxyindole-O-methyltransferase. On the other hand, VIP had no effect on the activity of arylamine-N-acetyltransferase. VIP increased the relative volume of rough endoplasmic reticulum, Golgi apparatus and mitochondria and did not influence the relative volume of lysosomes and lipid droplets as well as the numerical density of dense core vesicles in the examined rat pinealocytes. The obtained results indicate stimulatory effect of chronic treatment with VIP on the synthesis and secretion of melatonin in the rat pinealocytes in vitro. The results of morphological study are in agreement with the obtained biochemical data and point to the increase in secretory and metabolic activity of the rat pinealocytes in response to VIP.     

Effect of photoperiod on pineal gland volume and pinealocyte size in the Chinese hamster, Cricetulus griseus

Male adult (200-day-old) Chinese hamsters (Cricetulus griseus) raised from weaning under either LD 16:8 or LD 8:16 were used. The pineal gland of the Chinese hamster consists of superficial (major) and deep (minor) components and a continuous, or interrupted, narrow parenchymal stalk interposed between them. The volume of the superficial pineal including the parenchymal stalk is greater under LD 16:8 than under LD 8:16. Under both photoperiods, pinealocytes in the superficial pineal have larger nuclei and more abundant cytoplasm than those in the deep pineal. Nuclei in the superficial pineal appear pale and usually have irregular profiles, whereas those in the deep pineal appear dark and have round profiles. In the superficial pineal, pinealocyte nuclei are larger, paler, and more irregular; and, in addition, nuclear density is lower under LD 16:8 than under LD 8:16. Similar, but less prominent, photoperiod-induced changes occur in the volume of the deep pineal, the size of pinealocytes, and pinealocyte nuclear morphology in the deep pineal. The results indicate that the development and differentiation of pinealocytes in both pineal portions may be advanced under long photoperiods and delayed under short photoperiods, although pinealocytes in the deep pineal may remain not fully differentiated even in adults. Since testicular weights and body weights are similar under both photoperiods, the photoperiod may exert marked influences on the development of the pineal gland without affecting reproductive activity and growth rates of animals.     

Quantitative variations in nucleolar components within pineal gland cells during the rat estrous cycle

Quantitative changes in the size of pinealocyte nucleoli have been reported in various studies on this cell type. However, the significance of quantitative changes in the nucleolar components is unknown. The present study is an attempt to analyze ultrastructural and morphometric modifications occurring in the pinealocyte nucleolar components during the estrous cycle in female rats. The fibrillar centers showed an increase during estrus consistent with a decrease in pinealocyte nucleolar activity and melatonin pineal levels. The fibrillar components and granular components tended to display a reciprocal relationship. An increase in the dense fibrillar component took place at metaestrus and diestrus when melatonin synthesis increased in pinealocytes. Maximum values of granular and interstitial components were found at the proestrus phase before the day of ovulation.     

Influence of light/dark, seasonal and lunar cycles on the nuclear size of the pinealocytes of the rat

Morphological and physiological studies suggest a possible division of the pineal parenchyma into an external or "cortical" and another central or "medullar" layer. We have studied the possible influence of the light/dark, seasonal and lunar cycles on the nuclear size of the pinealocytes of the rat in both the hypothetical "cortical" and "medullar" layers. Forty male Wistar rats were used. Experiment was carried out in two seasons, winter and spring, two lunar phases, full moon and new moon, and the two circadian phases, photophase and scotophase. The nuclear volume of the pinealocytes, calculated from the Jacobj's formula, was the karyometric parameter used as measurement of the nuclear size. Main results showed that nuclear volume of the cortical pinealocytes was greater than that of the medullar pinealocytes only during the photophases of winter new-moon days and spring full moon days, whereas in all the remaining situations, the greater nuclear sizes were found in the pinealocytes of the medullar layer. These results support the existence of independent morphological variations of the pinealocyte in the central and peripheral zones of the pineal gland.     

蒙古黄鼠（Citellus dauricus）松果腺的超微结构观察

The distal part of pineal gland of the Mongolian ground squirrel was ultrastructurally studied. The gland was composed of low electron-dense parenchymal cells, among which glial cells, pigment cells, blood vessels and neural elements were occasionally interspersed. The pinealocytes contained numerous mitochondria, lysosomes, microtubules, microfilaments, Golgi apparatus and free ribosomes, as well as less prominent profiles of rough- and smooth-surfaced endoplasmic reticula and some cilia, centrioles, synaptic ribbons and few subsurface cisterns. Some pinealocytes were vacuolated. The content of the vacuoles released into the extracellular space by exocytosis could be observed. The gap junctions between pinealocytes were also observed. Of particular interest was that many mitochondria "fused together" and formed gap junction-like structure in about five percent pinealocytes. The pigment cell has a amorphous nucleus which contains many aggregated chromatin, its cell membrane has a few microvilli projecting into a central lumen, these features may indicated that this kind of cell differs either from the pinealocyte or astrocyte. There are axo-axonic synapses or axo-dendritic synapses between neuron processes or between neuron processes and pinealocytes.     

Effect of continuous darkness on circadian morphological rhythms in pinealocytes of the Chinese hamster,Cricetulus griseus

Summary Effects of a short-term exposure to continuous darkness on 24-h morphological variations in pinealocytes in the superficial pineal of the Chinese hamster (Cricetulus griseus) were examined. Pinealocytes contained type-1, -2 and -3 synaptic ribbons (SR), which had a central dense structure showing rod-like, various and ring-like profiles, respectively, and the quantity of each type of SR was expressed by SR index. 24-h changes in the type-1 and type-3 SR indices persisted in darkness and thus may be endogenous in nature. As under alternating light and dark (LD) conditions, the type-2 SR indices were almost constant over a 24-h period under continuous darkness, but the indices were larger in animals under darkness than in those under LD conditions. The 24-h variations in the nuclear and cytoplasmic volumes were abolished after exposing animals to darkness for 7 days, suggesting that these rhythms may be regulated exogenously. The amount of condensed chromatin exhibited a circadian change; this rhythm persisted under darkness. The results suggest that 24-h variations in the nuclear and cytoplasmic volumes in pinealocytes of the Chinese hamster are regulated by mechanisms different from those controlling the rhythms in SR and chromatin, and that the changes in the nuclear and cytoplasmic volumes and chromatin are related to the change in synthetic activity of pinealocytes.     

The pineal gland of the Indian palm squirrel, Funambulus pennanti (Wroughton)

In the adult palm squirrel, F. pennanti the pineal is a club shaped, elongated structure with a connective tissue capsule. It consists of various types of pinealocytes, glial cells, neurons, nerve fibres, blood vessels and connective tissue. Two types of pinealocytes could be identified by light microscopy. They are large rounded with centrally placed nucleus, and small rounded pinealocytes. They have medium sized processes stainable with Alcian blue, periodic acid Schiff and Nissl methods. The pinealocytes are not stainable with bromophenol blue. However, they are moderately stainable with PAS, Sudan black and Baker's acid hematin. Neurons are seen either singly or in groups with axonal processes. Cystic cavities often lined by cells are a normal feature of adult squirrel pineal, and the lining cells are both pinealocytes and glial cells. Often neuronal endings are seen terminating on these lining cells. PAS positive globules were also seen inside the cysts. In some squirrel pineals, fibrous cysts with an inner core of cells are also seen. Occasionally groups of lymphocytes were also encountered in the pineal. In the fetal pineal, the cells are both larger and smaller ones and arranged in a cortex and medulla pattern and no cystic cavities are seen. The third ventricle enters the base of the pineal as pineal recess.     

Body Size,Age Structure,Growth, and Maturation of Black Scorpionfish Scorpaena porcus (Scorpaenidae) from Southwestern Crimea (Black Sea)

Journal of Ichthyology - The body size and age structure, as well as the features of growth and sexual maturation, of black scorpionfish Scorpaena porcus from the coastal waters of southwestern...