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Striated muscle in the pineal gland of swine.

Striated muscle fibers (or cells) were observed in three of the six swine pineal glands. The muscle fibers occurred in clusters of several fibers about the parenchymal blood vessels. They were in general poorly developed, lacked regular cross striations and were not readily recognized histologically. The muscle fibers were, however, easily identified on electron microscopy because of the myofilaments they contain. In most of the muscle fibers, the myofilaments were arranged in ill-defined, disorderly bundles and rarely formed well-defined myofibrils and sarcomeres. The sarcotubular system was also poorly developed and triads were sparse and randomly scattered. Leptomeres were observed in several muscle fibers. The source of the muscle fibers in the pineal glands is not well understood and, whatever the source may be, the muscle fibers seem to remain poorly developed in the pineal glands.

Animals↗

PubMed1979

Evolution of the pineal gland in the adult chicken.

The structural pattern of the pineal gland in the hen corresponds to a more advanced stage of the evolution which began in an early period of the animal's life. This evolution corresponds mainly to the transformation of the large follicular cavities into cellular 'rosettes'. The parafollicular layer disappears from the rosette wall which thus remains with only one row of cells (A and B pinealocytes). The cellular hypertrophy and the great development of the pinealocyte organelles in the adult pineal gland makes us think of this gland as a functionally active organ. This functional activity must have remained during the entire period of the time studied (1--5 years), due to the ultrastructural uniformity found and due to the fact that we could not observe any type of degenerative process in the gland.

Acid Phosphatase↗

PubMed1995

Microvascularization of the pineal gland in the freshwater turtle, Pseudemys scripta elegans (Reptilia): a scanning electron microscopic study of vascular corrosion casts.

Gross supply, microvascular patterns, and drainage routes of the pineal gland and its vascular relations with associated structures (dorsal sac, paraphysis, choroid plexus of the third ventricle) were studied by scanning electron microscopy of microvascular corrosion casts in 10 specimens of the freshwater turtle, Pseudemys scripta elegans. Light microscopy of tissue sections (one transverse and one longitudinal series) served to attribute cast vascular territories to anatomical structures. The tubular pineal gland body is supplied bilaterally by small branches of the saccular artery, a branch of the lateral choroidal artery. Branches of the diencephalic artery supply the pineal stalk. The pineal gland microvascular bed is a two-dimensional network that embraces the tubular gland. The network is made up mainly of venules with few true capillaries. Venules draining the ventral surface of the pineal gland body join those coming from the choroid plexus of the third ventricle and drain into the sagittal sinus. The less dense vascular network embracing the dorsal surface of the pineal body drains directly into the sagittal sinus. The pineal stalk drains into the diencephalic vein or directly into the sagittal sinus. No efferent (venous) vascular connections capable as transport route for pineal secretions toward surrounding telencephalic, diencephalic, or mesencephalic areas were found.

Animals↗

PubMed2002

Control of postganglionic neurone phenotype by the rat pineal gland.

As neurones develop they are faced with choices as to which genes to express, to match their final phenotype to their role in the nervous system. A number of processes can guide these decisions. Within the autonomic and sensory nervous systems, there are a handful of examples that suggest that one mechanism that may match phenotype to function is the presence of target-derived differentiation factors. We tested whether the rat pineal gland controls the expression of a neuropeptide (neuropeptide Y) and a calcium-binding protein (calbindin) in sympathetic postganglionic neurones that innervate it. We first showed that the chemical phenotype of sympathetic neurones innervating the rat pineal includes the expression of both neuropeptide Y and the calcium-binding protein, calbindin. After transplanting the pineal gland of neonatal rats into the submandibular salivary gland of neonatal hosts, it was innervated by sympathetic axons from the surrounding salivary gland tissue, which do not normally express neuropeptide Y and calbindin. The presence of the pineal gland led to the appearance of neuropeptide Y and calbindin in many of the postganglionic neurones that innervated the graft. From these findings we suggest that, like the rodent sweat gland, the pineal gland generates a signal that can direct the neurochemical phenotype of innervating sympathetic neurones.

Animals↗

PubMed1999

Gene expressions of opioid receptors and G-proteins in pineal glands.

In our previous studies, the opioid receptors located on pinealocytes have been identified and characterized, and these receptors have been found to play a stimulatory role in melatonin synthesis by activating the rate limiting enzyme, N-acetyltransferase (NAT). In the present study, by using reverse transcriptase polymerase chain reaction (RT-PCR) followed by nested-PCR, segments of delta and mu opioid receptors have been amplified from mRNA of rat pineal gland and cerebral cortex. In addition, segments of delta and mu opioid receptors have also been amplified from mRNA of human pineal gland. Furthermore, G(alphai/o)- and G(beta)-protein-coupled receptor mRNAs have been amplified and identified from rat pineal gland. The regulatory effects of morphine on G(alphai/o) and G(beta) mRNA levels have been semiquantitatively analyzed. Acute morphine administration caused significant increase in G(alphai/o), and G(beta), mRNA levels in rat pineal gland, but not in other brain regions. Further studies are needed in order to elaborate the mechanisms of these opioid receptors in regulating G-protein expression in pineal gland.

Animals↗

PubMed1985

The presence of vasoactive intestinal polypeptide (VIP)-like-immunoreactive nerve fibres and VIP-receptors in the pineal gland of the Mongolian gerbil (Meriones unguiculatus). An immunohistochemical and receptor-autoradiographic study.

By use of the indirect peroxidase-antiperoxidase immunohistochemical technique, nerve terminals exhibiting vasoactive intestinal polypeptide (VIP)-like-immunoreactivity were demonstrated in the pineal gland of the Mongolian gerbil (Meriones unguiculatus). Incubation of the superficial pineal gland of the gerbil with 60 pM of 125I-VIP showed that the gland exhibited saturation kinetics, and about 80% of the bound 125I-VIP could be displaced by adding a surplus of cold VIP. Incubation of unfixed, 0.1% and 4% paraformaldehyde-fixed cryostat sections of the gerbil forebrain with 125I-VIP also exhibited saturation kinetics, and displacement was possible by adding a surplus of the cold tracer. Receptor autoradiography on cryostat sections that had been incubated for 60 min with 125I-VIP showed a large number of grains over cortical areas, especially over the pyramidal layer of the hippocampus and the granular layer of the dentate gyrus. A prominent labelling of the pineal gland was also observed. The presence of VIP-like-immunoreactive nerve terminals and receptors for this molecule in the pineal gland of the Mongolian gerbil supports the biochemical studies demonstrating a stimulatory function of this molecule in the synthesis of melatonin.

Animals↗

PubMed1995

Hydroxyindole-O-methyltransferase gene expression in the pineal gland of chicken embryo: development of messenger RNA levels and regulation by serum.

Hydroxyindole-O-methyltransferase (HIOMT), the enzyme which catalyzes the final step of melatonin biosynthesis, constitutes a marker of the functional differentiation of pineal cells. In addition, a day/night rhythm of HIOMT mRNA concentration, previously described in the chicken pineal gland [6], would suggest that HIOMT gene transcription is one output of the circadian system that controls pineal function. The study sought to monitor the developmental expression of HIOMT mRNA in the chick pineal gland and to investigate a possible role of instructive signals in this differentiation process. RT-PCR analysis indicated that HIOMT mRNA is expressed at embryonic day 8 (E8). At E12, HIOMT mRNA became detectable on northern blots and traces of HIOMT activity could be measured. HIOMT mRNA concentration increased 100-fold between E14 and day 10 post-hatch, then levelled off. A day/night rhythm of HIOMT mRNA concentration was readily observed in the pineal gland of 2-day-old chicks. Pineal glands isolated on minimum culture medium at E11 stopped developing HIOMT gene expression. However, the addition of serum to the culture medium restored HIOMT mRNA concentration to the levels observed in vivo. The data suggest that the functional differentiation of melatoninergic cells observed during the second week of embryonic life may be controlled [correction of controled] by serum factors.

Acetylserotonin O-Methyltransferase↗

PubMed2002

Pineal gland hormone and idiopathic scoliosis: possible effect of melatonin on sleep-related postural mechanisms.

Experimental and clinical evidences indicate that endocrine mechanisms, particularly involving the pineal gland, exert a role in the development of postural deficits leading to the occurrence of idiopatic scoliosis (IS). In particular, experiments performed in bipedal animals have shown that removal of the pineal gland, which secretes melatonin (M), induced a scoliosis, and that in such preparations, administration of this hormone prevented the development of this deformity (cf. 131). It appears also that adolescents with IS showed a reduced level of serum M with respect to age-related control subjects. The possible mechanisms involved in the M regulation of the tonic contraction of the axial musculature have been discussed. It is known that the pineal gland is implicated in the control of circadian rhythms, including the sleep-waking cycle, and that during this cycle there are prominent changes in postural activity, which affect not only the limbs, but also the axial musculature. These changes are characterized by a decrease followed by a suppression of postural activity, which occur particularly during transition from wakefulness to synchronized sleep and, more prominently, to rapid eye movement (REM) sleep. Episodes of postural atonia may also occur during the cataplectic episodes, which are typical of narcolepsy. Cholinergic and/or cholinoceptive neurons located in the dorsal pontine reticular formation (pRF) and the related medullary inhibitory reticulospinal (RS) system, intervene in the suppression of posture during REM sleep, as well as during the cataplectic episodes which occur in narcolepsy. These structures are under the modulatory (inhibitory) influence of the dorsomedial and the dorsolateral pontine tegmentum, where serotoninergic raphe nuclei (RN) neurons and noradrenergic locus coeruleus (LC) neurons are located. We postulated that M may act not only on the circadian pacemaker, but also directly on the pontine tegmental structures involved in the regulation of posture during the animal states indicated above. This hypothesis is supported by the facts that: 1) the dorsal pRF may contain specific binding sites for M; 2) this structure is particularly sensitive to M in adolescents, as well as in adult subjects affected by narcoleptic disturbances leading to cataplexy; 3) M increases the release of serotonin (5-HT), a neurotransmitter which enhances the postural tone by acting on the dorsal pRF: on the other hand, deficits in M levels may lower the activity of the serotoninergic raphe system, thus leading to a decrease or suppression of postural activity similar to that occurring either during REM sleep or during the cataplectic episodes typical of narcoleptic patients; 4) IS patients may show episodes of sleep apnea, a phenomenon which has been attibuted to a reduced tonic contraction of primary and accessory respiratory muscles during REM, resulting from a reduced release of 5-HT at dorsal pontine level. It has been postulated that, if the reduced M and 5-HT levels are subliminal to produce a complete suppression of posture under the conditions reported above, the reduced postural tone, which results from this condition may lead to the development of IS, due to hypotonia which affects the axial musculature. M secretion could be regulated not only by the activity of the serotoninergic raphe neurons projecting to the pineal gland, but probably also by the activity of noradrenergic LC neurons. It is likely that the development of IS, which results from a reduced level of M and 5-HT, may occur provided that the noradrenergic LC inhibition of the pontine structures is impaired. Such impairment could depend upon genetic factors, similar to those postulated to play a role in narcolepsy. In conclusion, the possibility exists that an impaired activity of brain monoaminergic systems may lead to disfunction in the production of M, which is apparently an important factor in the etiopathogenesis of IS.

Animals↗

PubMed1991

Benign symptomatic lesions of the pineal gland. Report of seven cases treated surgically.

Seven patients with non-neoplastic symptomatic lesions of the pineal gland have been operated on in our department since 1988. Clinical symptoms were slight and there were intermittent signs of a space occupying lesions in the quadrigeminal area, i.e. visual and gait disturbances. In three patients, obstructive hydrocephalus with related symptoms was found. Diagnosis was confirmed by use of MRI in sagittal planes, revealing a cystic lesion in five and a solid tumour in two patients. All patients were operated on without complications using an infratentorial supracerebellar approach. Histological examination showed glial cysts of the pineal gland in five patients. In the two solid specimens, normal pineal tissue was found. These lesions seem to be of special interest, as the only pathological property are their size: Both lesions--"too large pineal glands"--caused obstruction of the outlet of the third ventricle with subsequent hydrocephalus. Surgical treatment was curative in all cases with prompt relief of the symptoms. Clinical symptoms and signs, diagnostic and pathological findings, as well as the surgical results of these cases will be reported.

Adult↗

PubMed1983

Electrical responses to direct and indirect photic stimulation of the pineal gland in the pigeon.

Spontaneous electrical activity was recorded from pineal cells in intact and blinded pigeons. Modification of the activity by photic stimulation applied to the lateral eyes or directly to the pineal gland was observed in both groups of birds. The pattern of responses was different in the blinded compared to the sighted pigeons. In the birds with intact lateral eyes, the majority of responses to light were excitatory while in the blinded group more inhibitory effects were recorded. The results indicate that cells in the pigeon pineal gland retain a photoreceptive capacity although the sensitivity of the responsive units is low.

Animals↗

PubMed1979

Concentration of 5-methoxytryptophol in pineal gland and plasma of the rat.

5-Methoxytryptophol, a serotonin metabolite, was measured by gas chromatography-mass spectrometry in pineal glands, plasma and control tissues (cerebral cortex and salivary glands) from male rats kept in a controlled lighting environment. In the pineal gland the level of 5-methoxytryptophol was significantly higher during the dark period than during the light, the absolute levels being an order of magnitude less than those of melatonin. In the plasma, the levels showed a reverse situation with respect to lighting conditions. No correlation was found between the 5-methoxytryptophol levels in plasma and the pineal gland in individual animals. These results suggest that there is no obvious correlation between pineal content and pineal activity. This may be due to a combination of rapid turnover, secretion and/or peripheral conversion of another 5-methoxyindole to 5-methoxytryptophol.

Animals↗

PubMed1983

Mitotic activity and its 24-hour rhythm in the rat pineal gland.

Previous studies have yielded equivocal results concerning the 24-hour rhythmicity of mitotic activity in the rat pineal. The aim of the present study was to re-investigate this problem by carrying out three separate 24-hour experiments on alternate days. The results obtained confirm previous findings showing that in the pineal gland of adults mitotic activity is low. On average 22.3 mitotic figures of pinealocytes are seen per pineal gland, corresponding to a mitotic index of 0.2-0.6/1,000 pinealocytes. Mitotic activity is distinctly higher at daytime than at night. The timing of the peaks and troughs differs slightly from experiment to experiment. The majority of observations now indicate that in the rat pineal gland mitotic activity is higher at day time than at night.

Animals↗

PubMed2004

Effect of dark exposure in the middle of the day on Period1, Period2, and arylalkylamine N-acetyltransferase mRNA levels in the rat suprachiasmatic nucleus and pineal gland.

The suprachiasmatic nucleus (SCN) of the mammalian hypothalamus contains a central circadian pacemaker, which adjusts circadian rhythms within the body to environmental light-dark cycles. It has been shown that dark exposure in the day causes phase shifts in circadian rhythms, but it does not induce changes in the melatonin levels in the pineal gland. In this study, we examined the effect of dark exposure on two "circadian clock" genes Period1 and Period2 mRNA levels in the rat SCN, and on Period1, Period2, and arylalkylamine N-acetyltransferase (Aa-Nat, the rate-limiting enzyme in melatonin synthesis) gene expression in the pineal gland. Period1 and Period2 mRNA levels were significantly decreased in the SCN after 0.5 and 2 h, respectively, therefore suggesting that changes in those mRNA levels may be the part of the mechanisms of dark-induced phase shifts. Period1 and Aa-Nat mRNA levels in the pineal gland were not affected by darkness, but Period2 was moderately affected. Since Period1 and Aa-Nat mRNA levels in the pineal gland did not respond to dark stimulation, we further examined whether the pineal gland itself is capable of responding to adrenergic stimulation at this time of the day. Isoproterenol significantly induced Period1 and Aa-Nat mRNA levels; however, it did not affect Period2. Although previous studies have reported that during the day the SCN "gates" the dark information reaching the pineal, our data demonstrate that dark information may reach the pineal during the daytime.

Animals↗

PubMed2000

Effect of immunization on nocturnal NAT activity in chicken pineal gland.

OBJECTIVES: The effect of a single immunization with sheep red blood cells (SRBC) on the nocturnal NAT activity in the pineal gland and serum anti-SRBC agglutinin titer was examined in the young, sexually immature ASTRA S chickens. METHODS: 3-, 4-, and 5-week-old birds of both sexes, hatched in long (Spring) and short (Autumn) day, were housed from hatching in controlled light (L:D = 12:12) and temperature conditions. Quantity of produced 14C-labeled N-acetyltryptamine was used as a measure of the nocturnal NAT activity in the pineal gland. Serum anti-SRBC agglutinins were determined by microhemagglutination test. RESULTS: In experimental conditions applied, a sexual dimorphism in both pineal gland function and immune system activity was observed. NAT activity was dependent on the season, sex and age of chickens examined and was modified by the single immunization with SRBC. CONCLUSION: Results obtained confirmed once again the existence of the reciprocal functional connection between the pineal gland and immune system in chickens and demonstrated that even in well controlled experimental conditions the influence of the seasonal factor(s) on immunity must be taken into consideration.

Journal Article↗

PubMed1995

The pineal gland, cataplexy, and multiple sclerosis.

Since the discovery of melatonin as the principal hormone of the pineal gland in 1963, scientists have come to recognize that melatonin is a "master hormone" involved in the control of circadian rhythms and other biological functions. Although little is known about the influence of the pineal gland on motor control, important clues may be obtained by considering the pattern of melatonin secretion during the sleep cycles and particularly during rapid eye movement (REM) sleep when melatonin plasma levels are at their lowest. Since REM sleep is characterized by the occurrence of profound atonia which results in an almost complete paralysis of striated muscles, it is suggested that there might be a causal relationship between inhibition of melatonin secretion during REM sleep and the development of REM sleep atonia. This relationship is supported by the findings that melatonin regulates the activity of brainstem serotonin (5-HT) neurons which characteristically cease to fire during REM sleep and which faciliate the development of REM sleep atonia. Moreover, as the muscular atonia of REM sleep is physiologically and pharmacologically indistinguishable from cataplexy, it is possible that the pineal gland also influences to the development of cataplexy. Cataplexy is an ancillary symptom of narcolepsy and also occurs in multiple sclerosis (MS). In fact, it is believed that several of the neurological symptoms experienced by patients with MS such as weakness in the legs, feeling of collapsing knees, paroxysmal sudden falling, weakness in the neck, extreme fatigue, intermittent paresthesias, slurring of speech and intermittent blurring of vision, which often are exacerbated by stress and other emotional influences, may reflect the manifestations of cataplexy. Thus, several of the clinical features of MS may reflect a dissociated state of wakefulness and sleep and may improve by the administration of anticataplectic drugs.

Cataplexy↗

PubMed1993

Synaptophysin--a common constituent of presumptive secretory microvesicles in the mammalian pinealocyte: a study of rat and gerbil pineal glands.

Recent studies have established that pinealocytes of the mammalian pineal gland contain marker molecules of neuroendocrine cells or paraneurons like the synaptic vesicle-associated protein synaptophysin (p38). The objective of this study was to identify the subcellular synaptophysin-positive compartment and to characterize in detail the intracellular distribution of this protein in rat and gerbil pinealocytes. An analysis of serial semithin sections of plastic-embedded pineals immunostained for synaptophysin, including computer-assisted optical density measurements of synaptophysin immunoreactivities, demonstrated unequivocally that synaptophysin was highly concentrated in dilated process terminals of the pinealocytes. More than 75% of these process terminals were found to border or lie within the pericapillary space. At the ultrastructural level, they contained accumulations of small clear vesicles of variable size that turned out to be the site of synaptophysin immunoreactivity when immunogold staining was performed. In addition, microvesicles surrounding synaptic ribbons were also immunolabeled. Hence, the pinealocyte is the first neuroendocrine cell type that has now been shown to concentrate synaptophysin-positive microvesicles in perivascular process endings. This observation lends strong support to the hypothesis that small clear vesicles in neuroendocrine cells in general, and in pinealocytes in particular, serve secretory functions. The quantitative analysis of completely sectioned process endings revealed that the microvesicles outnumber by far the amount of dense core vesicles and therefore cannot arise by endocytosis of dense core vesicle membranes. Thus, small synaptic-like vesicles probably constitute an independent secretory pathway of the paraneuronal pinealocytes. In the present study, we could also establish the absence of immunoreactivity for synapsin I (belonging to a family of neuron-specific nerve terminal phosphoproteins) from pinealocytes. Synapsin I immunoreactivity was only detectable in intrapineal nerve terminals and varicosities. Taken together, the immunostaining patterns of the pineal gland obtained with antibodies directed against synaptic vesicle-associated proteins render the mammalian pinealocyte a very special type of neuroendocrine cell or paraneuron rather than a "classic" neuron.

Animals↗

PubMed1987

Gonadal regression induced by caloric restriction is not mediated by the pineal gland in deer mice (Peromyscus maniculatus).

The role of the pineal gland in mediating reproductive regression in response to nonphotoperiodic cues was assessed. A proportion of deer mice (Peromyscus maniculatus) undergo gonadal regression subsequent to moderate food restriction. The reproductive regression after inanition qualitatively and quantitatively resembles short-day-induced regression. The physiological mechanisms responsible for gonadal regression after food restriction are unknown. The hypothesis that the mechanisms underlying photoperiodic responsiveness also mediate testicular regression caused by reduced food consumption was tested. Males were pinealectomized or received sham operations. Upon recovery, food availability was restricted to 70% of ad libitum intake. After 8 weeks, the reproductive condition was examined. Pinealectomy did not prevent gonadal regression, suggesting that the pineal gland does not mediate caloric information in this species.

Animals↗

PubMed2001

Incorporation, distribution, and metabolism of polyunsaturated fatty acids in the pineal gland of rainbow trout (Oncorhynchus mykiss) in vitro.

The in vitro incorporation of 3H-radio-labeled arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids by the photosensitive trout pineal gland was visualized using photon and electron microscopy. After 6 hr of incubation, 3H-20:4n-6 appeared distributed in photoreceptors, as well as in glial cells, whereas 3H-22:6n-3 was preferentially taken up by photoreceptors, mainly in the apical part (including the photoreceptive outer segment). Radioactivity was mainly seen over membranes of glia when the incorporation of 3H-20:4n-6 was followed by 12-18 hr of chase. We also report differences in the incorporation of 14C-radio-labeled linoleic (18:2n-6), linolenic (18:3n-3), eicosapentenoic (20:5n-3), 20:4n-6, and 22:6n-3 acids into the lipids in glands cultured under different lighting regimes. Phosphatidylcholine and triacylglycerols contained most of the radio-labeled polyunsaturated fatty acids (PUFA) incorporated. The proportion of incorporated 20:4n-6 recovered in phosphatidylinositol was always significantly higher than that found with the other PUFA. At least 10% of radioactivity from each incorporated substrate, except 22:6n-3, was recovered in elongation products. It is concluded that the pineal gland of the trout can assimilate exogenous PUFA into cellular lipids in vitro, in a manner consistent with our previous in vivo findings. In terms of lipid composition, the trout pineal gland resembles more the vertebrate retina than the rat pineal gland. This might be related to the loss of direct photosensitivity of the mammalian pineal. Together, the differences reported herein between 22:6n-3 and 20:4n-6 suggest the former plays an important role in the phototransduction process, whereas the latter might be more specifically involved in the production of phosphoinositide-derived second messengers.

Animals↗