Embryonic development of pineal gland vesicles: a morphological and morphometrical study in chick embryos.

Pineal cell aggregates in 5, 10 and 15 day-old chick embryos have been studied. Cell aggregates were classified into rosettes or vesicles and spheroid and ellipsoid vesicles distinguished. The number of pineal vesicles per unit of surface (vesicle density) was determined in three pineal portions: apical, anterior and posterior. By day 5, only cellular rosettes were found, mainly in the apical portion. After 10 and 15 days, the presence of rosettes was occasional. The posterior wall showed only small spheroid vesicles, while in the apical and anterior areas ellipsoid vesicles were also observed. Moreover, the spheroid/ellipsoid vesicle ratio increased from the 10th to the 15th day of incubation. The vesicle density decreased between the 10th and 15th day because of the increase in both vesicle and pineal size, without changes in the total number of vesicles. The results suggest that changes in vesicle morphology and density could be related to the functional activity of the pineal gland during embryonic development.     

Pineal peptides in the regulation of milk-ejection reflex in lactating rats

The effects of pineal peptides (mol. mass 1-4 kDa) intranasal infusions on some parameters of milk-ejection reflex were investigated. Peptides were extracted from dairy-cattle pineal glands. Pineal peptides increase body weight, levels of water intake, plasma prolactin concentration and milk yield in rats when infusing daily in dose 1 microgram/kg from the third day of lactation. On 9th and 12th days of lactation during 1-hour nursing seance the significantly greater number of reflective milk ejections were found. When 1 hour before the peptides infusion rats were intraperitoneally injected by rabbit antiserum to oxytocin (200 microliters at dilution of 1:20) the effects of pineal peptides were significantly less expressive or were absent at all. Using enzymimmunoassay it was demonstrated that there were greater increasing of oxytocin content in pineal gland in suckling-induced oxytocin release from neurohypophysial system in the chronic pineal peptides-treated female rats compared with control. This effect was absent when rats were injected by oxytocin antibodies. These data suggest that pineal peptides can participate in forming of reflect oxytocin release pattern. This pattern is initiated by suckling and is limited by oxytocin content in blood.     

Differential permeability of pineal capillaries to lanthanum ion in the rat (Rattus norvegicus), gerbil (Meriones unguiculatus) and golden hamster (Mesocricetus auratus)

Summary Capillaries in the pineal gland of the rat (Rattus norvegicus), gerbil (Meriones unguiculatus) and golden hamster (Mesocricetus auratus) were investigated by means of electron-microscopical tracer studies using lanthanum. The tracer was administered together with the fixative solution by perfusion via the left cardiac ventricle. In the rat, endothelial junctions of fenestrated capillaries are permeable to lanthanum. In the gerbil the tracer does not leave the capillaries, which are of the non-fenestrated type throughout the organ. In the golden hamster the two portions of the pineal system have different types of capillaries. While in the superficial pineal fenestrated capillaries permeable to lanthanum predominate, the deep pineal possesses capillaries that are, without exception, devoid of fenestrations and impermeable to the tracer. It is suggested that differences in the structure of the capillaries are related to differences in the extent of a specialized contact of the pineal gland to the third ventricle.The authors dedicate this paper to Professor H. Rollhäuser, Münster, on the occasion of his 65th birthday     

Development of the innervation in the human pineal organ

Summary This investigation is concerned with pineal organs of human embryos 60 to 150 days old. At every stage central nerve fibres enter the pineal organ by way of the habenular commissure, but are restricted to the pineal's proximal part. On about the 60th day of the development the sympathetic nervus conarii grows into the distal pole of the pineal organ from a dorso-caudal direction and plays the predominant part in the innervation of the pineal organ. After penetrating, it soon branches out and forms a network in the pineal tissue. Much later, not until the 5th embryonic month, sympathetic nerves appear accompanying the supplying vessels in the perivascular spaces. After a short time these nerves pierce the outer limiting basement membrane and penetrate the parenchyma. Towards the end of the 5th embryonic month the axons of the sympathetic nerves form varicosities containing clear and dense core vesicles. At this point large amounts of laminated granules appear primarily in cell processes, probably of pinealocytes. Isolated granules also occur in the varicosities of axons. The granules encountered here are most likely secretory granules.Dedicated to Professor Bargmann on his 65th birthday.     

Role of tissue interaction between pineal primordium and neighboring tissues in avian pineal morphogenesis studied by intraocular transplantation

Tissue interactions play an essential role in organogenesis during embryonic development. However, virtually no attempts have been made to study the role of tissue interaction in pineal development. In the present study we examined the inductive role of the epidermis and mesenchyme in the morphogenesis of quail pineal glands. The pineal rudiment is first observed at embryonic day 2 (E2: 2 days of incubation) at the dorsal midline of the diencephalon as a short semi-spherical protrusion. Electron microscopic observations revealed that no mesenchymal cells are found between the epidermis and the distal end of the E2 pineal primordium but that a thin layer of mesenchymal cells separate the epidermis from the pineal primordium at E3. Small pieces containing pineal rudiment were cut off from E2 or E3 embryos. They were treated with enzymes to eliminate the epidermis and/or mesenchyme, grafted into E5 chicken eyes, and cultured there for 1 week. When E3 pineal rudiment was treated with Dispase to remove the epidermis, the pineal gland developed normally. When the rudiment was further treated with collagenase to remove the surrounding mesenchymal cells, a multi-follicular structure was still formed, but to a lesser extent than when rudiments were treated with Dispase alone. When E2 quail pineal rudiment with the epidermis was grafted without any treatment, a multi-follicular structure developed which morphologically resembled embryonic pineal organs. When the epidermis was removed from E2 rudiments by Dispase, a single large vesicular structure was formed. These results suggest that the overlying epidermis and/or mesenchymal cells play some inductive role in the initial pineal development, while the mesenchymal tissue plays an important role in pineal follicular formation later during development. Since only a few experimental studies have been done to examine pineal morphogenesis, the present study provides fundamental insights into avian pineal development.     

Ultrastructural observations at pineal gland capillaries in four rodent species.

The fine structure of the capillaries of the pineal glands of the rat, mouse, chinchilla, and ground squirrel were investigated. The pineal endothelial cells in the rat, mouse and ground squirrel were often composed of attenuated cytoplasmic portions which contained numerous fenestrations, in contrast to pineal capillaries in the chinchilla which were lined by thick non-fenestrated endothelial cells. Marked morphological differences were also apparent in terms of the types of vesicles within the cytoplasm and abutting on the cell surface of pineal endothelial cells from the various species investigated. The interendothelial junctions exhibited remarkable species differences with the chinchilla pineal possessing typical tight endothelial junctions while those in the rat, mouse and ground squirrel lacked such endothelial cell associations. Generally, capillary lining cells in the chinchilla pineal resembled similar cells within the brain, while endothelial cells in pineal glands of rat, mouse and ground squirrel were more typical of those found in other endocrine organs. Species differences in the structure of the pineal capillaries may represent physiological differences as well.     

Postnatal development of the dog pineal gland. Light microscopy

The light microscopical morphology of the dog pineal gland from the first postnatal day to maturity is described. In the first postnatal week, the pineal parenchyma shows immature cells and many mitotic figures. In this week, pigmented cells are observed for the first time, both in the pineal gland and in extrapineal nodules. Throughout the second week, the pineal parenchyma shows a cordonal pattern that disappears progressively in the following stages. From the 20-30th day onward, it is feasible to discern the cell types characteristic for the adult pineal gland. In the adult animals, the length of the pineal gland axes almost quadruplies that of the pineal gland in neonatal stages. The light microscopical features of the adult dog pineal gland are also described.     

Postnatal appearance of luteinizing hormone-releasing hormone (LHRH)-like material in the pineal gland of the rat

Summary Immunoreactive luteinizing hormone-releasing hormone (LHRH)-like material has been demonstrated in the pineal gland of the adult rat. The objective of the present study was to examine the ontogenetic development of this LHRH-like substance in the rat pineal with the peroxidase-antiperoxidase (PAP) method of Sternberger. LHRH-like immunoreactive material was not observed in pineal glands of newborn rats. The amount of material increased progressively from the 6th–12th day of postnatal development. On day 12, the amount of LHRH-like immunoreactivity was consistent and comparable in all pineal glands of male and female animals examined.Supported by NIH Grant 1 R01 HD-12956     

Prenatal Entrainment of Rat Testicular Malate Dehydrogenase Activity Circadian Rhythm

In mammals the photoperiodic synchronization of circadian system starts before birth. During fetal and neonatal period mothers relay the photoperiodic information to their litter. The maternal pineal melatonin 24 h cycle acts as a synchronizing signal. We have studied the effect of pineal maternal sympathetic denervation and administration of melatonin to mothers denervated during gestation on the prenatal synchronization of testicular malate dehydrogenase (MDH) activity circadian rhythm of the offspring 25 days after birth. When mothers were denervated at the 7th, 10th or 11th day of gestation, pups showed disruption of testicular MDH activity circadian rhythms. In contrast, no disruptive effect was observed when the mothers were denervated on the 12th or 14th day of gestation. When denervated mothers (7th day of gestation) were treated with a daily dose of melatonin from the 11th to the 14th day of gestation, pups showed a MDH activity circadian rhythm. The hormone failed to impose a daily phase when administered from the 9th to the 12th day of gestation. Results suggest that prenatal synchronization in the rat occurs very early in the development, before suprachiasmatic nuclei morphologic arrangement and functional activity begin.     

Postnatal development of the rabbit pineal gland. A light- and electron-microscopic study.

The development of the rabbit pineal gland has been studied by light and electron microscopy from the 1st to the 120th postnatal day. After 24 h of postnatal life, the pineal parenchyma is highly cellular, showing two identifiable cell types: pinealocytes I and II. Immature type II pinealocytes arrange either in cellular cords or clusters or forme rosette-like structures. At the 5th postnatal day, corticomedullar differentiation is established. Rosette-like structures and cellular cords are absent from the cortex. Along the postnatal period, nuclei of pinealocytes are set apart due to cytoplasmic widening and development of cell processes. These structures pervade the cellular cords and rosette-like structures formed by immature type II pinealocytes. Rosette-like structures are no longer seen beyond the 30th postnatal day, and cords of type II pinealocytes from the 90th postnatal day on. At this time, the rabbit pineal gland is considered to be histologically mature.     

Prenatal Entrainment of Rat Testicular Malate Dehydrogenase Activity Circadian Rhythm

In mammals the photoperiodic synchronization of circadian system starts before birth. During fetal and neonatal period mothers relay the photoperiodic information to their litter. The maternal pineal melatonin 24 h cycle acts as a synchronizing signal. We have studied the effect of pineal maternal sympathetic denervation and administration of melatonin to mothers denervated during gestation on the prenatal synchronization of testicular malate dehydrogenase (MDH) activity circadian rhythm of the offspring 25 days after birth. When mothers were denervated at the 7th, 10th or 11th day of gestation, pups showed disruption of testicular MDH activity circadian rhythms. In contrast, no disruptive effect was observed when the mothers were denervated on the 12th or 14th day of gestation. When denervated mothers (7th day of gestation) were treated with a daily dose of melatonin from the 11th to the 14th day of gestation, pups showed a MDH activity circadian rhythm. The hormone failed to impose a daily phase when administered from the 9th to the 12th day of gestation. Results suggest that prenatal synchronization in the rat occurs very early in the development, before suprachiasmatic nuclei morphologic arrangement and functional activity begin.     

Time course of angiogenesis in solid pineal autografts

Angiogenesis and reperfusion of blood vessels were analysed qualitatively, at the light- and electron-microscopical levels, in solid pineal autografts placed intracerebrally in adult rats (post-transplantation survival times: 1, 3, 7, 10, 14 and 28 days). Reperfusion of blood vessels was studied in sections from immersion-fixed brains incubated to demonstrate the endogenous peroxidase activity of erythrocytes within the lumen of blood vessels. The possible presence of the blood-brain barrier (BBB) within the grafts was also investigated by injecting native horseradish peroxidase (HRP) intravenously into the rats. Angiogenesis, the morphological and functional properties of blood vessels vascularizing the grafts and the survival of pineal tissue were analysed ultrastructurally following transplantation. Revascularization of pineal autografts placed into the adult host central nervous system occurred very slowly, requiring 7–10 days to establish anastomoses between graft and host blood vessels. During this process, signs of angiogenesis in pineal and cerebral capillaries were evident, suggesting that both contributed to graft revascularization. Morphological and functional studies with HRP revealed that, following transplantation, blood vessels at the graft-host interface or within pineal autografts maintained their morphological and functional properties: they were fenestrated and did not present a BBB to blood-borne peroxidase. Thus, after grafting, the presence or absence of the BBB is graft-determined. Revascularized pineal tissue showed good survival and pinealocytes revealed structural features of active secretory cells.     

Putative cholinergic elements in the photosensory pineal organ and retina of a teleost,Phoxinus phoxinus L. (Cyprinidae)

Summary Putative cholinergic neurons in the photosensory pineal organ of a cyprinid teleost, the European minnow, were studied by use of choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry. Pinealofugally projecting neurons were visualized using retrograde HRP-filling through their cut axons. For comparison, the distribution of choline acetyltransferase immunoreactivity (ChAT-IR) and AChE-positive elements in the retina was investigated.While the distributional patterns of ChAT-IR and strongly AChE-positive perikarya in the retina are similar and may represent the same neuronal population, ChAT-IR and AChE-positive elements in the pineal organ appear to belong to separate populations. In the retina, small- to medium-sized perikarya in the inner nuclear layer, and small perikarya in the ganglion cell layer are ChAT-IR and AChE positive. The entire inner plexiform layer is AChE positive, while only sublaminae 1, 2 and 4 are ChAT-IR. No indication of cholinergic activity was observed in the optic axon layer.In the pineal organ, ChAT-IR is restricted to small perikarya situated rostrally and dorsally in the pineal end-vesicle. AChE-positive neurons are present throughout the pineal end-vesicle and the pineal stalk. The pineal tract (the pinealofugally projecting axons of intrapineal neurons) is strongly AChE positive, but displays no ChAT-IR. The distribution of pinealofugally projecting neurons, labeled with retrogradely transported HRP, is markedly dissimilar to that of the ChAT-IR elements. It is proposed that the photosensory pineal organ transmits photic information to the brain via a non-cholinergic pathway. The possibility that the ChAT-IR neurons represent small local interneurons is discussed in the light of comparative physiological and anatomical findings.     

Light and electron microscopic studies on the pineal organ of the dogfish,Scyliorhinus canicula L.

Summary The pineal organ of the dogfish,Scyliorhinus canicula, is a long, thin, tubular structure consisting of an end-vesicle and a stalk. The pineal parenchyma consists of receptor cells, glycogen-storing cells, supporting cells, cells containing dense granules of 1,500–3,000 Å diameter, cytosome-rich cells, and ganglion cells. The latter alledgedly give rise to the diffusely distributed pineal tract which runs to the posterior commissure. A few pineal fibres diverge to the habenular commissure. The receptor cells have well-developed outer segments with morphological features characteristic of the retinal cone. Interaction between receptor cells and ganglion cells take place in neuropil-like areas. Boutons are found which are believed to belong to the receptor cells because of the presence of occasional synaptic rods. The few synapses observed always display synaptic vesicles both pre- and post-synaptically. The functional significance of the reported morphological features is discussed with the aid of the pertinent literature and it is postulated that the pineal organ of the dogfish is a photosensitive organ.Work done with the aid of a research scolarship from the Alexander von Humboldt Foundation, Bad Godesberg, Germany. — The animal material was provided by the Stazione Zoologica di Napoli, Italy, and by the Biologische Anstalt, Helgoland, Germany. — The electron microscope used in this study was placed at the disposal of Prof.Oksche by the Deutsche Forschungsgemeinschaft.     

脊椎动物松果器官的形态结构比较和演化初探

对脊椎动物６个纲中日本七鳃鳗、鲫鱼、黑斑蛙、丽斑麻蜥、家鸽和高原鼠兔等几种动物松果器官的形态结构进行了观察和比较,并对其演化作了初步探讨。脊椎动物的松果器官分为二大类,一类为变温动物的松果器官,由副松果体和松果体构成,其中副松果体是一个典型的光感受器,松果体亦主要具有感光的结构。另一类为恒温动物的松果器官,仅包含松果体,无副松果体,其结构主要具有内分泌腺的特征。在系统演化中,后一类松果器官可能是由前一类演变来的。从演化揭示：最早脊椎动物的松果眼是２个。哺乳动物的松果腺是由一种光感受器演变来的。     

Neuroendocrine integrative mechanisms in mammalian pineal gland: effects of steroid and adenohypophysial hormones on melatonin synthesis in vitro

The time course for the decrease in norepinephrine concentration of rat pineal explants in culture indicated a significant fall starting at the 4th hour and completed after 16-24 h of incubation. Significant decreases of serotonin and 5-hydroxyindoleacetic acid (HIAA) levels in tissue, an increase of HIAA/serotonin ratio, and an increase of melatonin production rate in vitro were also observed as a function of the incubation time. Estradiol (10(-7)-10(-5) M) increased rat pineal melatonin content, testosterone (10(-5) M) decreased it and progesterone was devoid of activity when incubated with explants for up to 6 h. The in vitro stimulatory effect of estradiol on rat pineal methoxyindole synthesis was blocked by propranolol but not by phentolamine; propranolol also blocked the increase of nuclear estradiol-receptor complex produced by estrogen exposure of pineal explants. TSH (1-100 ng/ml), growth hormone (10-100 ng/ml) and LH (10 ng/ml) augmented rat pineal melatonin content while 100 ng/ml of FSH decreased it significantly. Prolactin exerted a biphasic effect on rat pineal explants, the lowest concentration augmenting melatonin content while the high concentration depressed it. Deep, intermediate and superficial segments of guinea-pig pineal glands showed an increase in melatonin concentration after a 6-h incubation in the presence of 10(-7)-10(-5) M estradiol.     

Locally synthesized angiotensin modulates pineal melatonin generation

We aimed to study the mechanisms and the significance of the influence exerted by the renin-angiotensin system (RAS) on the pineal melatonin production. Pineal melatonin and other indoles were determined by HPLC with electrochemical detection after angiotensin AT1-receptor blockade with Losartan in vivo or in cultured glands. N-acetyltransferase (NAT) activity was radiometricaly measured. To test the in vivo relevance of the local RAS, pineal melatonin and its indole precursors were determined in transgenic rats with inhibited production of angiotensinogen exclusively in astrocytes, TGR(ASrAOGEN). Tryptophan hydroxylase (TPH) and NAT mRNA levels were determined by real-time RT-PCR. Pineal melatonin content was significantly decreased by AT1-receptor blockade in vivo, in cultured glands and in TGR(ASrAOGEN) (35%, 32.4% and 17.5% from control, respectively). Losartan produced a significant decrease of pineal 5-hydroxytryptophan, serotonin, 5-hydroxyindole acetic acid and N-acetylserotonin in pineal cultures. Also, the pineal content of the precursor indoles in TGR(ASrAOGEN) rats was significantly lowered. The reduction of 5-hydroxytryptophan levels by 33-75% in both in vivo and in vitro studies suggests a decreased activity of TPH. Moreover, the TPH mRNA levels in TGR(ASrAOGEN) rats were significantly lower than control rats. On the other hand, NAT activity was unaffected by Losartan in pineal culture and its expression was not significantly different from control in TGR(ASrAOGEN) rats. Our results demonstrate that a local pineal RAS exerts a tonic modulation of indole synthesis by influencing the activity of TPH via AT1-receptors.     

高原鼠兔松果体超微结构的研究

本文采用光镜和透射电镜对高原鼠兔松果体的形态结构进行了观察,并对其结构与功能的关系怍了初步探讨：1． 高原鼠兔的松果体与其他哺乳动物的基本相似, 包括深、浅两部分, 两部分的细胞构筑及其形态基本一致,主要由松果体细胞、胶质细胞、神经细胞、微细血管和神经纤维组成。松果体细胞有明、暗两种,两种细胞胞质内均有丰富的线粒体、高尔基复合体、粗面和滑面内质网,以及游离核糖体,还可见极少数微管和脂滴等。2． 松果体细胞内囊泡、微管和突触带的数量与细胞的分泌功能密切相关。3． 松果体分泌物主要通过二种方式释放：(1)通过扩散和胞吐作用,将分泌物释放到细胞外或血管周隙;(2)分泌物直接进入第三脑室。