Membrane bounded dense bodies (MBB) of the domestic pig pinealocytes--current state of knowledge.

The results of our former investigations concerning the pig pinealocyte organelles named membrane bounded dense bodies (MBB) have been summarized. The presence of MBB is the most conspicuous morphological feature of pinealocytes of genus Suidae. The relative volume of MBB in the cell bodies of pinealocytes in adult domestic pigs ranges from 8% to 16% of whole cytoplasm. On the basis of their morphology, membrane bounded bodies were divided into two main types: MBB-1 and MBB-2. Dense bodies of MBB-1 type have various inner structure and are present both in perikaryons and processes of the pinealocytes. Dense bodies of MBB-2 type are characterised by regular, multilammellar structure and their presence is restricted to pinealocyte perikaryons. The origin and transformations of the MBB are enigmatic. The relative volume of dense bodies in the pig pinealocytes changes during postnatal development and under various physiological and experimental conditions. The system of dense bodies is controlled by sympathetic innervation and environmental light. Dense bodies are also influenced by changes in function of pituitary-gonadal axis in female pigs and by administration of melatonin. High number of the dense bodies in the pig pinealocytes, significant changes in their number and inner structure in various physiological and experimental conditions as well as their exocytosis from pinealocyte processes suggest that these structures are involved in secretory processes in the pig pinealocytes.

Effects of p-chlorophenylalanine, amiflamine and melatonin treatment on the ultrastructure of pinealocytes in Sus scrofa.

The effects of p-chlorophenylalanine (pCPA), amiflamine [Fla 336(+)] as well as melatonin (MEL) treatments on the ultrastructure of pinealocytes in immature female pigs were investigated. Treatment of pCPA-tryptophan hydroxylase inhibitor resulted in the presence of numerous membrane-bound bodies type 2, with long, narrow cisterns of endoplasmic reticulum and a large Golgi apparatus. Fla 336(+) selective MAO-A inhibitor influenced the system of dense bodies, mitochondria and lysosomes (increasing their relative volume). Injections of melatonin resulted in the appearance of numerous homogeneous, round, regular shaped structures surrounded by membrane cytoplasmic structures ('granules'). The results indicate that a peculiar system of cytoplasmic dense bodies may be involved in indoleamine secretion in the pig pinealocyte.

Cytochemical localization of monoamine oxidase in the pig pineal gland.

Monoamine oxidase plays an important role in the regulation of monoamine levels in the pineal gland by oxidative deamination of serotonin to 5-hydroxyindole acetic acid. The ultrastructural sites of this process are still not well known. In the present study the pig pineal glands were examined by using two cytochemical methods for demonstration of MAO activity at the ultrastructural level. The use of selective inhibitors of MAO-A (clorgyline and amiflamine) and MAO-B (deprenyl) showed that MAO-A was localized predominantly in noradrenergic nerve terminals as well as in the cell membrane of endothelial cells. MAO-B activity was localized in pinealocytes. However, in the outer membranes of cytoplasmic dense bodies, which are characteristic cytoplasmic structures of pig pinealocyte, we noticed the activity of both MAO-A and MAO-B enzymes. The MAO-A was localized exclusively in dense bodies within bulbous ending of pinealocyte processes present in the perivascular space. Our results show that in pig pineal gland there are two forms of MAO localized in different compartments of the pineal tissue. The most important result of our study is the presence of MAO in cytoplasmic dense bodies, which points to these bodies as to the sites of oxidative deamination and confirms their participation in the secretory process in pig pineal gland.

Distribution of calcified concretions and calcium ions in the pig pineal gland.

Serial sections of pig pineal glands were stained with von Kossa's and Alizarin red S methods to determine the occurrence and localization of calcified concretions. In the pineal glands of pigs aged eight months, concretions were not found. A small number of concretions was observed in all investigated pineal glands of three years old pigs. The concretions were distributed in the connective tissue of the pineal capsule and septa. The potassium pyroantimonate method was used for ultracytochemical localization of calcium ions. In pinealocytes, precipitates were observed in nuclei, mitochondria, Golgi apparatus, endoplasmic reticulum and cytoplasmic matrix. Single precipitates were found on the outer membranes of dense bodies, multivesicular bodies and lysosomes. There were no differences in the amount or the localization of precipitates between dark and light pinealocytes and between pinealocytes of animals aged both eight months and three years. The results suggest that: (1) the calcified concretions in the pig pineal gland are formed by the leptomeningeal tissue without participation of the pinealocytes, (2) cytoplasmic dense bodies, specific components of the pig pineal gland, are only slightly involved in calcium turnover in the pinealocytes.

Distribution of neuropeptide Y-like immunoreactivity in the hypothalamic tuberal nuclei of the immature gilts.

The distribution of neuropeptide Y in the immature female pig hypothalamic tuberal nuclei was investigated using avidin-biotin complex method. This study showed cell bodies containing NPY-immunoreactive material in the arcuate nucleus, dorsomedial and ventromedial nuclei, as well as internal layer of the median eminence and infundibulum, an observation not yet reported in the pig. NPY-immunoreactive fibers were noted throughout the hypothalamus, but most prominently within the periventricular region. Median eminence disclosed abundance of NPY-immunoreactive processes. The study shows a detailed organization of cell bodies and fibers containing NPY-immunoreactivity in tuberal hypothalamic nuclei of the immature gilts.

Effect of long-term administration of melatonin on ultrastructure of pinealocytes in gilts.

We studied the ultrastructural changes in gilts' pineal gland after the oral administration of melatonin in dose 3 mg once daily (in ethanol vehicle) for 46 consecutive days. Appearance of the pinealocytes containing numerous secretory granules and an enlarged Golgi apparatus was the most visible effect of the melatonin administration. The melatonin treatment caused also some differences in the structure of pinealocytes with cytoplasmic dense bodies. The present results suggest that the orally administered melatonin had some effects on pigs' pineal gland.

Effect of ovariectomy followed by administration of ovarian steroid hormones on the pig pinealocyte ultrastructure.

The ultrastructure of female pig pinealocytes was studied after ovariectomy alone and ovariectomy followed by administration of estradiol, progesterone, or both. Administration of estradiol as well as a combination of estradiol and progesterone induced qualitative ultrastructural changes in pinealocytes relative to Golgi apparatus and cytoplasmic dense bodies as well as quantitative ones, such as a decrease in relative volume of cytoplasmic dense bodies and lysosomes. Administration of progesterone caused the formation of dense bodies and a decrease in the relative volume of lysosomes. The results point to a relationship between the pineal gland and gonads in the pig and suggest that gonadal steroids, particularly estradiol, could be involved in a feedback mechanism of the hypothalamic-hypophyseal-gonadal system to the pineal gland.

Ultrastructure of the ram pinealocytes during breeding season in natural short and in artificial long photoperiods.

The study was performed from 20th September to 20th October on eight Polish Longwool rams, variety Pomorska (Pomeranian), aged 33 months, which were divided into two equal groups. The animals of control group were kept in natural photoperiod. The experimental group was maintained during 30 days in controlled lighting conditions (16L: 8D). On the thirtieth day of the experiment the animals were slaughtered between 1000h and 1200h. The pineal glands were prepared for EM. Point count analysis was employed to estimate the relative volumes of pinealocyte organelles. The increase of relative volumes of mitochondria and lipid droplets in comparison to the control was observed in the experimental group. There were also some qualitative changes in organization of granular endoplasmic reticulum and microtubules.

Influence of prolactin on ultrastructure of pinealocyte in sexually immature female pigs: a quantitative study.

The effects of long-term prolactin administration on the ultrastructure of pinealocytes in young female pigs were studied by means of morphometric analysis. Prolactin administration for 26 consecutive days resulted in an increase in the cytoplasmic dense bodies type MBB-1 and some differences in their structure. There were no significant changes in the other cytoplasmic structures. Prolactin appeared to stimulate the process of formation of dense bodies.

Effect of different diurnal lighting conditions on serotonin content in the pig pineal gland. Subcellular fractions of the tissue.

Serotonin content in the pineal glands and in their subcellular fractions of the pig housed under natural and limited to circa 2.5 hours per day lighting conditions has been examined spectrofluorometrically. The shortened circadian light phase caused dramatically high drop of serotonin content in the evening (1900-2000). Correlation between presence of dense bodies in subcellular fractions and content of serotonin has been not observed.

Influence of bilateral ovariectomy on the morphology and ultrastructure of the pineal gland in the pig (Sus scrofa)--quantitative and qualitative study.

Ovariectomy effects ultrastructure of pig pineal gland. It caused changes in both structure and number of cytoplasmic components and volume of nuclei. The most significant ones were observed two weeks after ovariectomy. The reported changes point to relationship between the ovaries and pineal in pig.

The effect of progesterone and progesterone + estradiol on the morphology of the pineal gland in immature female pigs.

Pineal gland of the immature female pigs treated with progesterone and progesterone and estradiol simultaneously were investigated with light and electron microscopy. Both of the applied hormones influenced the structure of the pineal glands. Inhibitory effect of progesterone on the relative volume of mitochondria, granular vesicles and dense bodies of type one was observed. Administration of progesterone and estradiol simultaneously caused more complicated influence statistically significant increase of pinealocyte nuclei volume and at the same time significant decrease of mitochondria and granular vesicles.

Ultrastructure of pig pinealocytes in various stages of the sexual cycle: a quantitative study.

Relative volumes of mitochondria (MIT), lysosomes (LYS), Golgi profiles (GP), granular endoplasmic reticulum (GER), membrane bound bodies of type 1 (MBB 1) and type 2 (MBB 2), and the number of dense-core vesicles (DCV), were counted in pinealocytes of female sexually immature pigs, in animals in oestrus and in nursing pigs. Relative volumes of GER, LYS, MBB I and the number of DCV changed in the different stages of the sexual cycle. The highest volumes of GER, LYS and MBB 1 were observed in pigs in oestrus. Pinealocytes of sexually immature pigs were characterized by a considerably higher number of DCV in comparison with mature animals.

The pineal gland of the red deer male. Histology and ultrastructure with notes on the fallow deer and mouflon pineals.

The most conspicuous morphological feature of the investigated red deer pineal gland was very deep pineal recess, covered with continuous layer of the ependymal cells. Its branches (2-3) reached the distal part of the gland. The slight differences in pineal structure of sexually active and sexually inactive red deer were observed. Relatively large pineal glands both of mouflon and fallow deer showed many common as well as different structural features.

The ultrastructure of capillary walls and perivascular space of the pineal gland in three representatives of suidae species.

The ultrastructure of capillary vessels and the perivascular space (PVS) of the pineal gland were investigated in the domestic pig, miniature pig, and wild boar. It has been ascertained that the capillaries of these animals have continuous thick walls without pores and fenestrations. In fetal period, capillaries with spacious lumina, bordered by 3 to 4 endothelial cells predominate. The PVS, as a rule wide open, contain nerve endings, pinealocyte process endings, and collagenous fibers which increase with age.

Morphology of the pineal gland in pregnant and nursing sows.

The pineal glands of pregnant and nursing sows were studied by light and electron microscopy. Similar structural changes in the pineal gland during pregnancy and lactation were noted as follows: a proliferation of glial cells concurrent with a decrease in the number of pinealocytes, a relative increase in the number of pinealocytes with cytoplasmic accumulation of dense bodies, and an increase in number of presumptive microglia. It appears that pregnancy and lactation exert a complex influence on pineal function, with a predominantly stimulating effect.