Showing papers on "Pinealocyte published in 1984"

Multiple redundant circadian oscillators within the isolated avian pineal gland

Abstract: The avian pineal gland contains a circadian pacemaker that oscillates in vitro. Using a flow-through culture system it is possible to measure melatonin production from very small subsections of an individual gland. We have used this technique to attempt to localize the oscillators in the pineal. Progressive tissue reduction did not affect the rhythmicity of cultured pineals. Multiple pieces (up to eight) from a single pineal all were capable of circadian oscillation — establishing directly that a pineal gland contains at least eight oscillators. All pineal pieces were responsive to light, and single light pulses shifted the phase of the melatonin rhythm. Because pieces equivalent to less than one per cent of the whole gland were rhythmic and because the capacity for oscillation was distributed throughout the gland, an individual pineal appears to be composed of a population of circadian oscillators.

Pineal indoles: production, secretion and actions

Abstract: Publisher Summary This chapter discusses pineal indoles, its production, secretion, and actions. The biochemical events involved in the conversion of tryptophan to various pineal indole products have been clarified. After the amino acid is taken up by the pinealocyte from the systemic circulation, which provides a perfuse blood supply to the pineal gland, it is hydroxylated in the 5 position to 5-hydroxytryptophan by the enzyme tryptophan hydroxylase (L-tryptophan, tetrahydropteridine: oxygen oxireductase); this enzyme requires both molecular oxygen and reduced pteridine as cofactors. Blood levels of melatonin have been more difficult to quantitate than has the content of this compound in pineal tissue. The presence of melatonin in the blood and either its reduction after pinealectomy provided the proof that the indole was secreted from the gland and also assured the pineal endocrine status.

Evolution of the pineal complex: correlation of structure and function.

Abstract: The pineal organ is a derivative and integral component of the brain. In phylogeny it has changed from a 'third eye' capable of direct achromatic and/or chromatic responses to light to an endocrine gland influenced by visual stimuli from the retina. The outer segment of pineal photoreceptors contains a microspectrophotometrically detectable photopigment and an opsin-immunoreactive protein. Certain pinealocytes endowed with an outer segment display fluorophores of 5-HT/HTP and can be regarded as photoneuroendocrine cells. These photoneuroendocrine cells resemble cerebrospinal fluid-contacting neurons. The intrinsic circuitry (wiring diagram) of pineal photoreceptor organs has been only partly deciphered ; this holds true also for the neurotransmitters and synaptic patterns. Pineal photoreceptor organs are connected to the brain, i.e., to habenular, pretectal, thalamic, tegmental (reticular), and hypothalamic centers. The special anatomical and physiological features of the pineal organ enable it to translate photic information into neural and neuroendocrine responses.

Ultrastructure of the pineal gland in the adult rat.

Abstract: The ultrastructure of the rat pineal gland was studied from 75 days until 10 months of age. Type I pinealocytes of young adults showed nuclei with dispersed chromatin, numerous infoldings of the nuclear envelope and well developed nucleoli. The cytoplasm displayed many mitochondria and clusters of smooth endoplasmic reticulum. With increasing age, there was a clear increase in the number of dense bodies or lysosomes in the Type I pinealocyte. The changes in the Type II pinealocytes with age were mainly in nuclear shape and in the appearance of lipofuscin granules.

Postnatal evolution of the rat pineal gland: light microscopy.

Abstract: The postnatal development and morphology of the adult albino rat pineal gland was studied from one day up to ten months of age. During postnatal life there was a marked increase in gland and pinealocyte volume, more intense during the first 45 days. After ten days, the differences in nuclear morphology of parenchymal cells showed two different types of pinealocyte. The characteristic adult arrangement of pinealocytes in cords and pseudo-rosettes was observed after 15-20 days. After 75 days there was a progressive increase in the number of connective tissue fibres.

Electrophysiological properties of rat pinealocytes: evidence for circadian and ultradian rhythms.

Abstract: Extracellular single-unit recordings were made during day- and night-time in the pineal gland of urethane-anesthetized adult male Sprague-Dawley rats. All cells exhibiting spontaneous electrical activity had firing frequencies from less than 1 Hz to about 100 Hz, and their discharge patterns were characterized as regular, irregular or bursting. While most of the spontaneously active cells (n=63) showed a uniform activity level throughout the recording period (30–120 min), a group of 9 cells exhibited oscillatory rhythms with periods of 4–8 min. In addition, long-term recordings across day- and night-time from five cells revealed increasing activity during night-time in three cells, while the remaining two units showed constant activity throughout the recording time (8–20 h). Comparison of day- and night-data in general indicated an overall higher level of activity at night.

Day/night changes of pineal gland volume and pinealocyte nuclear size assessed over 10 consecutive days.

Abstract: Previous studies aimed at elucidating day/night changes of pineal gland size and pinealocyte nuclear volume have yielded contradictory results The aim of the present investigation was to examine the above parameters over a period of 10 successive days, at 6-hour intervals under a lighting regimen of LD 12∶12 (7 am to 7 pm) It was found that changes in pineal gland volume could not be correlated with the light/dark phases; instead, a rhythm with a two-day period was encountered Pinealocyte nuclear volume, by contrast, showed clear circadian changes, exhibiting troughs during photophase and peaks during scotophase

Interstitial and parenchymal cells in the pineal gland of the golden hamster. A combined thin-section, freeze-fracture and immunofluorescence study.

Abstract: A combined thin-section/freeze-fracture study was performed on the superficial pineal gland of the golden hamster, comparing the parenchymal and interstitial cells of this animal with those previously investigated in rats. In contrast to rats, no gap junctions and gap/tight junction combinations could be found between pineal parenchymal cells of the hamster. Furthermore, the interstitial cells of the hamster pineal gland were found to have large flat cytoplasmic processes, which abut over large areas equipped with tight junctions. In thin sections, profiles of interstitial cell processes were seen to surround groups of pinealocytes. Interstitial cells and their sheet-like, tight junction-sealed processes thus appear to delimit lobule-like compartments of the hamster pineal gland. Because the classification of the interstitial cells is uncertain, the expression of several markers characteristic of mature and immature astrocytes and astrocyte subpopulations has been investigated by indirect immunohistology. Many of the non-neuronal elements in the pineal gland are vimentin-positive glial cells, subpopulations of which express glial fibrillary acidic protein (GFA) and C1 antigen. The astroglial character of these cells is supported by the lack of expression of markers for neuronal, meningeal and endothelial cells. M1 antigen-positive cells have not been detected.

Ultrastructural characterization of glial cells in the rat pineal gland with special reference to the pineal stalk

Abstract: In the present study the "interstitial" cells of the superficial pineal gland and the nonparenchymal cells of the pineal stalk in Sprague-Dawley rats were examined ultrastructurally with the aim of defining the cells more closely. The "interstitial" cells of the superficial pineal gland do not represent a homogeneous cell population. The most abundant cell type is the mononuclear phagocyte, most easily recognized by its dark appearance and its content of primary and conspicuous secondary lysosomes. Astrocytes can be distinguished by the typical appearance of their nuclei (i.e., a thin continuous rim of heterochromatin adjacent to the nuclear membrane), identical to that of astrocytes in the CNS. Depending on the absence or presence of glial filaments and their amount, a spectrum of astrocytic cells is present. Mature astrocytes with filaments throughout their cytoplasm are rare. Immature glial cells with few or no filaments predominate. In the vicinity of blood vessels pericytes are present. In view of the fact that the "interstitial" cells could generally be identified it is suggested to abandon the term interstitial for the cells in question. In the pineal stalk mature astrocytes predominate; they have some features in common with pinealocytes, i.e., the presence of intergrade endoplasmic reticulum and grumose bodies (lysosomes). Other unusual features are a relative abundance of coated pits and vesicles. Oligodendrocytes are restricted to the proximal part of the stalk, near the deep pineal, where myelinated axons are abundant. More distally a few Schwann cells were seen.

Structure and ultrastructure of the aging rat pineal gland.

Abstract: The pineal gland of rats 12-28 months old was studied with light and electron microscopes. All pineal components exhibited regressive changes of different intensity with age. In type I pinealocytes, there was a marked increase in dense bodies as well as the occasional appearance of wide cell profiles full of vesicles. Type II pinealocytes showed nuclear infoldings and cytoplasmic deposits of lipofuscin. Pineal stroma displayed an increase in connective tissue fibers, both collagen and oxytalan, as well as remains of basement membranes and other materials of unknown nature. Calcareous concretions were also found, mostly in the pineal capsule. All regressive changes were more intense with increasing age.

Sensory and Central Nervous Elements in the Avian Pineal Organ

Abstract: The pineal organs of the adult domestic mallard, fowl and pigeon were investigated by means of neurohistological techniques and electron microscopy. The application of opsin immunocytochemistry to the pineal organ of the domestic mallard reveals antigenic sites in the outer segments of the pinealocytes. Avian pinealocytes may establish synaptic contacts to intrapineal neurons via complex neuropil formations. Bundles of nerve fibers resembling the pineal tract of poikilothermic vertebrates were found in the pineal stalk. These findings strengthen the view that the avian pineal organ has not lost its photoreceptive capacity.

Gap junctions between guinea-pig pinealocytes

Abstract: In accordance with previous results in rats, belt-like arrangements of fenestrated gap junctions have been found around the collicular segments of pineal cells in the guinea pig. In addition, macular interpinealocyte gap junctions have been observed in this species.

Cytochemical analysis of calcium distribution in the superficial pineal gland of the Mongolian gerbil.

Abstract: The potassium pyroantimonate-osmium method was employed to determine the distribution of cations in the superficial pineal gland of the Mongolian gerbil. The reaction product in the glands was presumed to be calcium following the use of both the chelator EGTA and x-ray microanalysis. A gradient of reaction product was found in the pineal with the highest concentrations occurring in and around the pineal concretions (PC). The periphery of mature PC demonstrated a heavy precipitate as did the surrounding pinealocytes. PC-associated pinealoeytes contained reaction product in many organelles, including small vesicles that appeared to be opening in the direction of the concretions. The vacuoles of the pinealocytes contained various concentrations of precipitate. The results obtained in the present investigation have led to a hypothesis on the formation of pineal concretions: (1) a pinealocyte vacuole is formed, (2) calcium is transported to the vacuole, (3) the cation content of the vacuole increases, and (4) the cations precipitate into an immature concretion. Fibrillar material and an amorphous substance located within the pinealocyte vacuole appear to form cation containing vesicles that contribute to the periphery of the developing PC, resulting in the continued growth of the concretion.

No correlation of pineal "synaptic" ribbon numbers and melatonin formation in individual rat pineal glands.

Abstract: As previous circadian studies of pineal "synaptic" ribbon numbers and melatonin formation suggested that a positive correlation of the two variables exists, in the present investigation this problem was examined in individual pineal glands of rats killed at 1200 h and 2400 h, respectively. For this purpose, one half of the gland was processed for electron microscopy and the ribbons were counted in an area of 20,000 micron2 tissue; in the other half serotonin N-acetyltransferase (NAT) activity and melatonin content were determined. No correlation was found to exist between ribbon numbers and pineal NAT activity, pineal melatonin levels and serum melatonin levels, either at day- or at nighttime. It is concluded that the ribbons may perhaps be more closely related to the innervation of the pineal gland than to melatonin formation.

Functional morphology of the pineal gland in young chickens.

Abstract: One and two-month-old chickens were killed at mid light and mid dark under the experimental photoperiod (LD 12: 12). The pineal glands of the young chickens are composed of parenchymal cells and large follicles, presenting a tubulofollicular arrangement. The sensory-like pinealocytes are pear-shaped and have a cilium with 9 + 0 axial configuration projecting into the lumen. Their cytoplasm has cell organelles, small granulated vesicles about 100 nm in diameter and synaptic ribbons. The concentric lamellar complexes like myelin sheaths are frequently observed in the follicular lumen. The secretory-like supporting cells have irregular-shaped microvilli and some granulated vesicles about 200 nm in diameter in the vicinity of the apical surfaces. Occasionally, a few nerve cells are found in the pineal parenchyma. It was found that the sensory-like pinealocytes of the young chickens have many mitochondria, well-developed Golgi complexes and large lysosomes in solid type in the light period, whereas they have a few cell organelles and somewhat smaller rod-like lysosomes with some vacuoles in the dark period. On the other hand, the sensory-like pinealocytes have more synaptic ribbons in the dark period than in the light period.

Day-night differences in estimated rates of 5-hydroxytryptamine turnover in the rat pineal gland

Abstract: Rates of 5-hydroxytryptamine synthesis in various brain tissues can be estimated from the linear increase in 5-hydroxytryptophan levels following inhibition of 5-hydroxytryptophan decarboxylation with RO4-4602 or NSD-1015. In addition, NSD-1015 can prevent 5-hydroxytryptamine oxidative-deamination via monoamine oxidase inhibition, leading to linear decreases in a major metabolite of this amine, 5-hydroxyindole acetic acid. In the rat pineal gland we demonstrated similar increases in 5-hydroxytryptophan levels after nocturnal or diurnal injection of RO4-4602 (100 mg · kg−1) or NSD-1015 (200 mg · kg−1). Similar decreases in 5-hydroxyindole acetic acid were also observed after nocturnal or diurnal injection of NSD-1015 or pargyline (an inhibitor of monoamine oxidase) (75 mg · kg−1). 5-Hydroxytryptamine levels increased after nocturnal pargyline injection but remained constant after diurnal pargyline administration. 5-Hydroxytryptamine levels exhibited little change following nocturnal injection of NSD-1015 but decreased linearly after diurnal injection of NSD-1015. We suggest that (1) rat pineal 5-hydroxytryptamine synthesis is increased nocturnally, (2) metabolic utilization, primarily by oxidative-deamination, of 5-hydroxytryptamine is increased diurnally and (3) basal levels of pineal 5-hydroxytryptamine may be stored within adrenergic nerve endings which innervate the pinealocytes responsible for synthesizing this amine, thus “protecting” or otherwise making unavailable this pool of 5-hydroxytryptamine for metabolic utilization.

Synaptic junctions between the adrenergic axon varicosity and the pinealocyte in the rat.

Abstract: Intercellular relationships of sympathetic nerve fibers and cells in pineal glands of Long-Evans rats and yellow-bellied country rats (Rattus losea Swinhoe) were studied with conventional electron microscopy. Typical synapses were found between adrenergic axon varicosities and pinealocytes. The synaptic cleft was 20-30 nm thick and contained granular or filamentous material of moderate electron density. Some small granulated vesicles attached to, or fused with, the presynaptic axolemma, a feature suggesting an exocytotic release of the vesicle content. The occurrence of membranous cisternae or tubules in the synaptic nerve ending may connote the phenomenon of synaptic vesicle recycling. Beneath the postsynaptic pinealocyte plasmalemma there was a dense plaque corresponding to the postsynaptic density of neurons. Possible origins and functional significance of the synapse-making nerve fibers are also discussed.

The ultrastructure of the nerve fibers and pinealocytes in the rat pineal stalk.

Abstract: In view of the increasing interest in the central innervation of the mammalian pineal gland, this aspect was studied in depth in the rat. This species is especially suited since the nerve fibers in question form a distinct bundle running from the deep to the superficial pineal gland through the pineal stalk. The axons were counted and analysed ultrastructurally in the pineal stalks cut transversely at three levels (proximal, intermediate, and distal) relative to the neural axis and in longitudinal sections. The number of nerve fibers was highly variable, ranging from 551 to 1, 132 proximally and from 110 to 448 distally, indicating that many fibers terminate in the stalk or leave the stalk after forming a loop. Large myelinated axons, which are abundant proximally, appear to lose their sheaths along their course through the stalk. Most of the axons were small and unmyelinated. A few of these had the appearance of sympathetic fibers and disappeared after sympathectomy. Others contained abundant neurosecretory granules, and, according to the literature, may originate in the hypothalamic paraventricular nuclei. The majority of the small axons which are apparently devoid of granules and dense-cored vesicles may come from the habenular nuclei and the stria medullaris. In addition to axons, the stalk contains astrocytes, a few oligodendrocytes and Schwann cells, as well as pinealocytes identical to those of the superficial pineal gland.

Effect of acute light exposure upon melatonin content, NAT activity, and nuclear volume in the gerbil pineal complex.

Abstract: This report describes the response of both the superficial and deep components of the gerbil pineal gland to a 30-min pulse of fluorescent light at the time of the nocturnal peak in pineal activity. When gerbils were maintained in a 14 h light:10 h dark photoperiod, mean melatonin concentrations in the superficial pineal gland ranged between 72 and 108 pg/gland during the day and first 4 h of darkness, rose to a peak of 399 pg/gland 7 h after lights out, then returned to basal levels at the expected time of light onset. Pineal melatonin contents were reduced to daytime values within 30 min after exposure of gerbils to fluorescent light at the time of the nocturnal peak. These changes in superficial pineal melatonin content reflected the circadian pattern in serotonin N-acetyltransferase (NAT) activity, as would be expected if NAT controls melatonin synthesis. In addition to the reductions in NAT and melatonin content induced by nocturnal photic stimulation, there was a 30% reduction in mean pinealocyte nuclear volume. A nocturnal elevation in melatonin content but not in NAT activity occurred in the deep pineal gland. Unlike the superficial pineal gland, the deep pineal gland did not demonstrate a response in melatonin content, NAT activity, or pinealocyte nuclear volumes upon exposure of gerbils to light at the time of the nocturnal peak in superficial pineal activity.

Morphometric analysis of the pineal complex of the golden hamster over a 24-hour light:dark cycle: II. The deep pineal in untreated and optically enucleated animals.

Abstract: The deep pineal gland of golden hamsters was morphometrically analyzed and quantitatively compared with the superficial pineal under a 14:10 lighting regime and following blinding. The deep pineal comprised 6-10% of the total pineal parenchymal tissue. Pinealocytes of the deep gland were smaller than the cells of the superficial pineal and showed a greater percent volume of Golgi bodies, rough endoplasmic reticulum, and dense-cored vesicles. Twenty-four-hour rhythms in nucleoli and Golgi bodies were found in deep pinealocytes. These rhythms were out of phase with comparable rhythms in the superficial pineal gland, suggesting that distinct subpopulations of pinealocytes are present within the respective parts. Blinding resulted in decreased nuclear and nucleolar volume, while the amount of smooth endoplasmic reticulum, Golgi bodies, dense bodies, and dense-cored vesicles increased significantly. Marginal increases were seen in mitochondria and lipid droplets. The greater abundance of those organelles involved in synthesis and secretion suggests enhanced cellular activity after blinding. Many of the morphological responses are similar to alterations in the pinealocytes of the superficial pineal following optic enucleation.

The pineal gland of the horse. Morphological and histochemical results. (With notes on the donkey and mule pineal).

Abstract: The horse pineal gland has been investigated by morphological and histochemical methods. Particular care has been given to the cellular types, to the eventual presence of neurosecretory activity and to the nature of the pigments. Even in the horse pineal, it is possible to distinguish two populations of pinealocytes, morphologically but not histochemically distinct. A great number of pinealocytes are positive for the Masson- Hamperl reaction, and for Gomori- Bargmann 's chromic haematoxylin-phloxine and Gomori's paraldehyde-fuchsin. Along the connective septa, many brown- blackish pigmented cells were present; their pigment was positive for the Lillie and the Masson-Fontana reactions for the determination of melanin pigment. Another type of pigmented cells, carrying a brown yellowish pigment of lipofuscin nature was present, particularly in older animals, along the connective septa.

Prior light alters the circadian clock in the chick pineal gland.

Abstract: N-Acetyltransferase activity (NAT) exhibits a circadian rhythm in the pineal gland and retinas of chickens and is responsible for melatonin circadian rhythms. Chick pineal gland NAT was measured in vivo and/or in vitro after light-dark cycles and after pretreatments with short photoperiod, long photoperiod, and constant light. Prior lighting changed the shape (phase, amplitude, and duration) of the rhythm in vivo. Some of the alterations are “programmed” into the pineal gland because they were observed in vitro in pineal glands from chicks similarly exposed to lighting pretreatments.

Morphodynamic response of the pineal gland to initial stress attack.

Abstract: The influence of an initial stress attack (a subcutaneous saline injection plus rough handling) on the morphofunctional behaviour of the pineal gland was studied. Both light and electron microscopy pointed to an enhanced endocrine activity on the gland parenchyma. The occurrence of the clusters of highly activated light pinealocytes, as well as the appearance of two functionally different types of these cells, revealed that the introduction of the pineal gland to a new stress-induced steady state was based on the gradual promotion of a number of pinealocytes to the level of a high activity. Dark pinealocytes were less numerous and rather engaged in the synthesis than in the secretion. The ultrastructural characteristics of both pinealocyte populations show that the pineal gland meets the secretory demands upon an initial stress attack by a striking discharge of its active compounds and a successive activation of a new elaborative cycle. The morphodynamic conclusion about an enhanced pineal gland secretory activity is fully evaluated in the change of the rate of prolactin surge. A possible impact of the morphodynamic reactivity of the endocrine parenchyma of the pineal gland upon the functional interpretation of the morphological properties of pinealocytes in case of some manipulative procedures with animals was discussed.

Seasonal variations in the cerebrospinal fluid-contacting area of the pineal gland in the golden hamster (Mesocricetus auratus).

Abstract: The cerebrospinal fluid-contacting area in the pineal recess of the golden hamster (Mesocricetus auratus) has been investigated light and electron microscopically. The results reveal that in this area the ventricular surface is composed of glial cell processes and protruding pinealocytes. The relative extent of these two components varies considerably and seems to be related to the season of the year: Morphometric analysis shows that in June, the mean size of the total cerebrospinal fluid-contracting area and, in addition, the relative extent of the area occupied by protruding pinealocytes is significantly larger than in November. The physiological significance of this finding remains to be determined.

Seasonal Changes in Glycogen Level and Size of Pinealocytes of the White‐Footed Mouse, Peromyscus leucopus: A Semiquantitative Histochemical Study

Abstract: Glycogen level in and size of pinealocytes of the feral, white-footed mouse Peromyscus leucopus, were studied by a semiquantitative histochemical method to determine whether seasonal changes exist in them under natural conditions, what temporal pattern they exhibit, and whether 24-hour changes in these parameters exist in different seasons, as shown in the laboratory dd-mice. Marked seasonal changes were seen in both glycogen levels and nuclear densities (ANOVA p less than 0.005). The size of pinealocytes at 09:00 to 10:00 showed one peak (and nadir) seasonal change, with the smallest size in winter (December and February) and a larger size in warmer seasons, with the maximum value in July. Glycogen level in pinealocytes at 09:00 to 10:00 showed bimodal seasonal changes, with lower levels in fall and spring and higher levels in winter and summer. In fall, a circadian trend in glycogen level in pinealocytes was seen, with a higher level at the end of the light period. In winter, the glycogen levels were very high at 09:00, 13:00, 17:00, and 21:00 examined and showed dampening of time-of-day differences. On the other hand, the size of pinealocytes followed a time-of-day change (P less than 0.005), being largest at 13:00 and smallest at 21:00. Thus, marked changes in quantitative structure and chemical activities, suggesting changes in functional activity, in pinealocytes were noted especially in severe, cold winter.

In-vitro uptake and metabolism of [3H]-5-hydroxytryptamine in the pineal glands of the rabbit, rat and hamster. A comparative study with the use of autoradiography, chromatography and liquid-scintillation counting.

Abstract: Pineal glands of rat, rabbit and hamster were incubated during day or night in Merlis' fluid containing [3H]-5-hydroxytryptamine (= [3H]-HT) by the use of a 20-min pulse with or without postincubation in “cold” medium for 15, 30, 45 or 60 min. (1) Selective autoradiographic labeling was observed in sympathetic nerve terminals; this reaction was missing after bilateral surgical removal of the superior cervical ganglia. In contrast, a scarce and diffuse labeling was found in pinealocytes (Pi) and interstitial cells (IC) of both untreated and ganglionectomized animals. (2) With the use of thin-layer chromatography, it could be shown in the rat that the well-known indoles of the pineal gland are formed from [3H]-HT. (3) During preparation for electron microscopy (EM), the total loss of indoles from pineal glands was studied by means of liquid-scintillation counting; approximately 57% of the radioactivity of the pineal glands was released into EM-processing solutions, mainly into the glutaraldehyde fixative.

Cyclic renewal of whole pineal photoreceptor outer segments.

Abstract: In the light-sensitive epiphysis cerebri of adult frogs (Rana esculenta) adapted in summer to an artificial long day (L:D = 17:7; L = 90 lx at 2,300°K; controlled temperature of 8°C) outer segments of cone-like pineal photoreceptor cells exhibit a cyclic and complete renewal. Shortly after ‘lights off’ inner segments protruding into the pineal lumen bear exclusively bulbous cilia of the sensory type. Considering these results, concepts dealing with different types of sensory pinealocytes have to be re-evaluated.

Pineal gland morphology in rats with experimentally induced protein-calorie malnutrition.

Abstract: The morphology of the pineal gland was studied in protein-calorie-malnourished (PCM) rats. Twenty-day-old male Sprague-Dawley rats were placed in a 14:10 photoperiod and fed either an 8% low protein diet (LPD) or a standard laboratory diet (SLD) containing 27% protein for 30 d. At 50 d of age, rats from both animal groups were sacrificed at 0900 h and at 2400 h, and the pineal glands were immersion-fixed for either light or electron microscopic analysis. The cytoplasm and nuclei of the pinealocytes from the SLD-fed rats were consistently larger than those of the animals maintained on the LPD. Additionally, the lipid droplets were larger and more prominent in the controls at both 0900 h and 2400 h. Even though the size of these inclusions did not vary among animals given the same diet as a function of the time of sacrifice, they were more numerous in both the well-fed and malnourished rats during the dark phase of the photoperiod. In contrast neither diet nor sampling time affected the size or number of pinealocyte mitochondria. These morphological observations lend further support to the premise than PCM impairs the cellular activity of the pinealocytes.

Effects of experimentally induced chronic hyperprolactinemia on the ultrastructure of pinealocytes in male rats

Abstract: The influence on the ultrastructure of pinealocytes of long-term hyperprolactinemia caused by ectopic pituitary transplants and of suppression of prolactin release by bromocriptine was examined morphometrically in male rats. Hyperprolactinemia resulted in an increase in the relative volumes of granular endoplasmic reticulum, vacuoles containing a flocculent material, mitochondria, and lipid droplets. Treatment of grafted rats with bromocriptine reversed the effects of hyperprolactinemia. However, bromocriptine had no apparent influence on the pinealocytes of intact rats. The effects of hyperprolactinemia on the ependymallike secretory process in the pinealocyte were especially pronounced.