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

Regional heterogeneity in immunoreactive macrophages/microglia in the rat pineal gland

Using specific macrophage antibodies (OX-42, OX-6, ED-1 and ED-2), this study examined the distribution of macrophages/microglia in the pineal gland of adult rats. Except for ED-2, all antibodies labeled distinct subpopulations of macrophages/microglia in the gland; ED-2 labeling was hardly detectable. The quantitative study showed that the pineal macrophages/microglia (PMM) expressing complement type 3 receptors (OX-42) were more numerous than those expressing the major histocompatibility complex class II antigen (OX-6) or unknown cytoplasmic/lysosomal antigens (ED-1). The PMM were ubiquitous, especially the OX-42 labeled cells which were distributed from the dorsal to the ventral aspect of the gland. The macrophages/microglia labeled with OX-6 or ED-1 were localized mainly in the intermediate portion of the pineal gland. Immunolabeled cells were sparsely distributed in the distal portion of the pineal gland. A notable feature was that the OX-6 labeled macrophages/microglia showed a proximal-distal gradient in cell density. Another interesting feature was the occurrence of prominent cell aggregations around the larger blood vessels. These cells were mostly round and exhibited different immunoreactivity. Confocal microscopic study with triple immunolabeling further revealed that individual PMM cell possessed two or more different antigens (ED-1+/OX-6+, OX-42+/OX-6+ or OX-42+/ED-1+). Remarkably, a large population co-expressed ED-1+/OX-6+/OX-42+. The present results show that the expression of immunoreactive molecules in PMM varies in topographical distribution of the cells. It is suggested that this may be linked to their immunoregulatory functions in the gland.

The production of scoliosis after pinealectomy in young chickens, rats, and hamsters

STUDY DESIGN

This study involved weekly radiographic examination of pinealectomized rats, hamsters, and chickens to observe the development of scoliosis.

OBJECTIVES

To determine whether pinealectomy produces scoliosis in animals more closely related phylogenetically to humans than to chickens, namely rats and hamsters, which are representative of mammals.

SUMMARY OF BACKGROUND DATA

Pinealectomy in 3-day-old chickens has consistently resulted in the development of scoliosis with many characteristics similar to those seen in patients with adolescent idiopathic scoliosis. It has not been determined whether this phenomenon is restricted solely to chickens or is applicable to other animals, especially those more closely related to humans.

METHODS

The pineal gland was removed from young rats, hamsters, and chickens. All animals underwent radiography weekly to detect the development of any scoliosis. Weight and length measurements were also taken weekly, and serum melatonin levels were determined at the time the animals were killed.

RESULTS

Scoliosis was not observed in either the rats or the hamsters. In contrast, scoliosis developed in 10 of 21 chickens. Serum melatonin levels in all pinealectomized animals were zero.

CONCLUSIONS

In contrast to the chickens, pinealectomy does not seem to cause scoliosis in either young rats or hamsters. The reasons for this discrepancy may include differences in the physiology and spinal morphology of the rat and hamster in comparison with the chicken. In the pinealectomized chickens, the results also suggest that future scoliosis development might be indicated by a significant increase in size when they are compared with pinealectomized chickens that do not develop scoliosis. Such differences in growth rates also distinguish patients with adolescent idiopathic scoliosis.

Quantitative light microscopic study on the heterogeneity in the superficial pineal gland of the rat

BACKGROUND

The previous results regarding regional and day-night differences in pinealocyte size in rats are conflicting. The relationships between these differences and the vascularity and sympathetic innervation have scarcely been investigated.

METHODS

Wistar-King rats, kept under light/dark 12:12, were killed at midday or midnight in October. The nuclear density of pinealocytes in the superficial pineal was measured on the dorsoperipheral, dorsocentral, ventroperipheral, and ventrocentral regions at distal, middle, and proximal levels at daytime and nighttime. The total area of blood vessels per unit area at daytime and nighttime and total length of tyrosine hydroxylase (TH)-immunoreactive fibers per unit area at daytime were determined on the same regions at the same levels.

RESULTS

Pinealocyte size was larger toward the distal levels and in the periphery than in the center at any level. The area of blood vessels and length of TH fibers were also larger toward the distal levels; the former in the ventral region and the latter in the dorsal and ventral regions were larger in the periphery than in the center. Ventral pinealocytes, but not dorsal ones, showed day-night changes in size. Prominent day-night rhythms in area of blood vessels occurred in the ventral region, where TH fibers were more abundant than in the dorsal region.

CONCLUSIONS

Pinealocyte size shows the distal to proximal and peripheral to central gradients, which may be related to the differential distribution of blood vessels and sympathetic fibers. Since pinealocytes and blood vessels, showing prominent day-night changes in size, are localized in the more richly innervated regions, sympathetic fibers may play an important role in controlling these rhythms.

Ultrastructure of the mammalian pinealocyte under natural and experimental conditions: quantitative aspects

This review briefly summarizes data accumulated on the quantitative aspects of the ultrastructure of the mammalian pinealocyte. Quantitative changes have been demonstrated under natural and experimental conditions in pinealocyte cell organelles in various species. Special attention is paid to two cytoplasmic components most frequently studied by means of quantitative electron microscopy, namely, dense-core vesicles and "synaptic" ribbons.

Pinealocyte subsurface cisterns. II: Influence of time of day, sympathectomy, and castration

Subsurface cisterns (ssc) of the gerbil pinealocyte were studied by electron microscopic morphometry taking account of different external influences: time of day, sympathetic deafferentation, castration with or without substitution of testosterone. Male individuals of Meriones unguiculatus, aged 150 days, were used. Though ssc number is invariant with respect to the light-dark cycle, ssc size follows a highly significant sinusoid curve. The largest ssc were found in the afternoon, the smallest ones in the early morning. Bilateral resection of the superior cervical ganglia reduces the density of pinealocyte ssc markedly, and their size is maximal or, in relation to the scaled-down cell, unusually large. Castration with or without application of testosterone propionate does not alter pinealocyte ssc, neither with respect to density nor size. From these experimental data it is concluded that pinealocyte ssc may play a supportive role in the regulation of pinealocyte sensitivity, in so far as it depends on receptors located in the cell membrane.

Comparison of the rat pinealocyte ultrastructure with melatonin concentrations during daytime and at night

The aim of this study was to investigate the ultrastructure of rat pinealocyte during daytime (1600 h) and at night (0100 h) and to compare these observations with serum melatonin levels in the same animals. In addition, pineal melatonin concentrations were determined in other animals. Both serum and pineal melatonin concentrations were significantly higher at night than during daytime (34 and 21 times, respectively). Sizes of pinealocytes, their nuclei, and nucleoli, as well as cross-sectional areas of mitochondria and granular endoplasmic reticulum were also higher at night than during daytime, whereas areas of lysosomes, Golgi apparatus, and vacuoles containing flocculent material did not differ at the time points studied. In contrast, the number of dense-core vesicles was higher during daytime. The results of the present study show that morphological patterns of higher metabolic activity of the rat pinealocyte at night when compared to those during daytime correlate with melatonin concentrations.

Comparisons of sizes of pinealocyte nuclei and pinealocytes in young and adult Chinese hamsters (Cricetulus griseus) under different photoperiod conditions

Semiquantitative electron microscopic observations on pinealocytes of the Chinese hamster (Cricetulus griseus) were made to compare the sizes of pinealocyte nuclei and pinealocytes as a whole, their nuclei and cytoplasm together, over a 24-hr period, between young animals (60-70 days old) and adult animals (120-130 days old) under LD 12:12 and between adults under LD 12:12 and LD 14:10. Under LD 12:12, similar 24-hr rhythms exist in the nuclear area and the area of pinealocytes of young animals, whereas in adults these values exhibit no significant 24-hr rhythm. In adults under LD 14:10, there is no significant 24-hr rhythm in the nuclear area, but the area of pinealocytes shows a statistically significant 24-hr rhythm. Thus, in the Chinese hamster, the relationships between nuclear area and area of pinealocytes with time of day vary, depending on the age of animals as well as different photoperiodic conditions, although they differ only slightly.

Pinealocyte dense-cored vesicles and synaptic ribbons: a correlative ultrastructural-biochemical investigation in rats and mice

Dense-cored vesicles (DCV) and synaptic ribbons (SR) were quantified in the pineal gland of the rat (Sprague-Dawley) and mouse (Sasco/ICR strain), and day/night differences in frequency of these organelles correlated with levels of indoles determined by high performance liquid chromatography (HPLC). There were significant day/night differences in levels of serotonin (5HT), 5-hydroxyindole acetic acid (5HIAA), N-acetyl-5HT, and melatonin in the rat gland. Melatonin and N-acetyl-5HT were not detectable in the mouse gland sampled every 4 h over the light:dark cycle. The concentrations of 5HT and 5HIAA (ng/microgram protein) were similar in light-adapted rats and mice, but these indoles did not exhibit a circadian rhythm in the mouse gland. Correlative ultrastructural/biochemical results suggest that DCV do not contain physiologically important stores of 5HT since 1) the mouse gland contains the same number of DCV as the rat during the daytime, but only one-tenth the levels of 5HT, 2) day/night 5HT levels do not vary in the mouse gland, but there is a significant nocturnal decline in DCV numbers, and 3) 5HT levels in the rat gland decline at night when DCV numbers increase. Numbers of SR were significantly elevated at night in the rat and mouse, and the frequency of this organelle was similar in both species. However, ribbon-type SR predominated in rat pinealocytes, whereas SR in the mouse were almost exclusively spherical in shape. Day/night differences in SR numbers in the mouse gland suggest that cellular mechanisms regulating the frequency of this organelle do not involve factors related to indole metabolism. Because of the lack of photoperiodic effects on indole metabolism in the mouse pineal gland, this species is a potentially important model to study the functional relationship of pinealocyte organelles to cyclical changes in pineal products other than indoles (e.g., peptide/protein factors).

Inverse behaviour of "synaptic" ribbon and spherule numbers in the pineal gland of male guinea-pigs exposed to continuous illumination

There is increasing evidence that pineal "synaptic" ribbons are a heterogeneous population of organelles. In addition to "synaptic" ribbons (SR) sensu stricto, which consist of an electron-dense rod surrounded by electron-lucent vesicles, "synaptic" spherules (SS) exist, the electron-dense core of which is round and much wider than that of the SR. In the guinea-pig SR and SS numbers exhibit an inverse day/night rhythmicity. To gain more insight into the functional significance of SR and SS, guinea-pigs were exposed to continuous illumination for approximately 4 months (LL) and the respective structures in the pineal gland were quantitated under the electron microscope and compared with control animals kept under a lighting regimen of 12 h light and 12 h dark. It was found that SR numbers increase following LL whereas SS numbers decrease. The proximal, intermediate and distal parts of the dumbbell-shaped organ respond differently. The increase in SR numbers is significant in the distal and intermediate regions only, whereas the decrease in SS numbers is significant in the proximal and the intermediate regions only. Within each pineal region analyses of parenchymal subareas measuring 65 microns by 65 microns exhibit an inverse correlation of SR and SS numbers indicating that there are parenchymal domains in which either SR or SS predominate. Morphometric analyses of a number of pinealocytic parameters reveal minor differences between different pineal regions and that exposure to LL does not strikingly affect the pinealocyte perikarya. By contrast, the numbers of pinealocyte processes increase significantly after LL in the distal and intermediate, but not the proximal region of the pineal gland.(ABSTRACT TRUNCATED AT 250 WORDS)

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

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.