Pituitary serotonin content: effects of melatonin or deprivation of water.

Relatively high concentrations of serotonin are found in the three regions of the rat pituitary gland. Administration of melatonin causes a selective increase in the serotonin concentration of the pars intermedia; deprivation of water for 5 days causes a selective decrease in the serotonin concentrations of the neural lobe and pars distalis.

Chromaffin reactions and fluorometric determination of catecholamines in the neonatal adrenal medulla of the rat.

Adrenaline and noradrenaline fluorometric determinations were simultaneously made in adrenal glands of 2-to-10 day-old rat with the histochemical localization of total catecholamines and noradrenaline. In 10-day-old-rats the increase is three times higher for adrenaline and four times higher for noradrenaline compared to 2nd day of age. Chromaffin cells of 2-to-10-day-old rats showed a low granular population preferentially located in the periphery of the cells. Seven days after birth the chromaffin granules were numerous and dispersed in extense areas of the cytoplasm. The dichromate reactions for total catecholamines were positive from the 5th day of age when the fluorometric determination was 250 ng of catecholamines (CA) per gland. The glutaraldehyde silver technique for noradrenaline was positive from the 7th day when the fluorometric determination was 35 ng of noradrenaline (NA) per gland. However, at the electron microscope level, this last reaction shows the same silver precipitates on the chromaffin granules in adrenal glands obtained from 4-to-6-day-old rats. These results indicate that the appearance and evolution of the chromaffin positive reaction during post natal development is a direct expression of molecular changes during maturation of the granular complex.

Comparative effect of insulin and explanted adrenal medullary tissue and rat adrenal medulla in situ.

The adrenal medulla and explanted medullary cells in the anterior chamber of the eye were examined 3 h after the administration of insulin to rats. No alterations were seen in the explanted cells. In the adrenal medulla, light and electron microscopy indicated depletion of adrenaline cells; noradrenaline cells were not affected. Levels of catecholamines were three times higher in the explanted tissue after insulin treatment; in the medulla in situ they declined by 70%. These results confirm that insulin has no direct releasing effect on chromaffin cells.

Cell populations in the pineal gland of the viscacha (Lagostomus maximus). Seasonal variations.

Pineal samples of the viscacha, which were taken in winter and in summer, were analysed using both light and electron microscopy. The differences found between the two seasons were few in number but significant. The parenchyma showed two main cell populations. Type I cells occupied the largest volume of the pineal and showed the characteristics of typical pinealocytes. Many processes, some of which were filled with vesicles, could be seen in intimate contact with the neighbouring cells. The presence in the winter samples of "synaptic" ribbons and spherules, which were almost absent in the summer pineals, suggests a seasonal rhythm. These synaptic-like structures, as well as the abundant subsurface cisterns present in type I cells, appeared as basic differential features which allowed these cells to be distinguished from type II cells. These latter cells, which can be classified as interstitial cells, showed some other distinguishing features, such as irregular-shaped nuclei, abundant deposits of glycogen-like particles and structures of unknown function consisting of concentric cisterns surrounding a dense body. In the summer, interstitial cells displayed numerous large round bodies, which contributed to increase the cellular volume slightly. Regarding other constituents, like glial cell processes, vessels of non-fenestrated endothelium and sympathetic innervation, no qualitative differences were observed between the two seasons studied. We have presented here some morphological evidences of the circannual rhythm of the viscacha pineal, as well as ultrastructural criteria for distinguishing the main cell populations of this organ, which could be useful for studies carried out in other mammals.

Neonatal and adult adrenal cortex: intercellular permeability to nickel nitrate.

The intravascular perfusion of nickel nitrate-glutaraldehyde showed a free penetration into neonatal and adult adrenal cortex. Tracer deposits were found surrounding the cortical cells without interruption; they formed a permeate network of intercommunicated intercellular spaces in connection with the vessels. No penetration of the tracer was observed between the chromaffin cells of the medulla. During the first day after birth, canalicular structures appeared among the cortical cells. In the adrenals of 4 and 7-day-old rats the lateral contacts between adjacent cells were more extensive. In 10-day-old rats nickel delimited the cellular profile, revealing numerous infolded cellular membranes. Gap and septate-like junctions were present. In the adult rats the structure of the cell membrane was unfolded. The observations made in adrenal cortex of 10 and 90-day-old rats perfused with lanthanum hydroxide were similar to those on nickel-treated material. The structural characteristics of this network of intercommunicated spaces and the attachments between cortical cells change during neonatal development, probably favoring cell interactions.

Seasonal changes of the Leydig cells of viscacha (Lagostomus maximus maximus). A light and electron microscopy study.

The Leydig cells of viscacha (seasonal rodent) show cytoplasmic hypertrophy and regional distribution during the breeding period (summer-autumn). The dominant organelles are smooth endoplasmic reticulum (SER) and mitochondria. A moderately well-developed Golgi, abundant lipid inclusions, dense bodies like lysosomes in different stages, and centrioles are observed. Extensive or focal desmosome and gap-like junctions between neighbouring Leydig cells are present. These cells exhibit an evident hypotrophy and an increase in the number of dense bodies during the gonadal regression in winter (July and August). Cells in different stages of involution are observed in this period. Their nuclei are irregular and heterochromatic. The cytoplasm contains few mitochondria. The vesicular SER is scarse. Irregular and large intercellular spaces with microvilli and amorphous material are present. The junctional complexes are absent. The nuclear and cytoplasmic volume and development of SER and mitochondria increase during the recovery period (spring). The lipid inclusions decrease. Dilatations of the intercellular space with microvilli and limited by focal desmosome-like junctions are observed. In conclusion, the Leydig cells of Lagostomus maximus maximus show deep changes alongside the reproductive cycle. The photoperiod variations, through pineal hypothalamus pituitary axis and the hormone melatonin, are probably responsible for them. Moreover, the fall of serum and tubular testosterone would be one of the factors responsible for gonadal regression.

Probable effect of photoperiod on seasonal variation in the nuclear volume of the adrenal cortex of viscacha (Lagostomus maximus maximus).

The neuroendocrine system regulates several organic functions such as reproduction, metabolism and adaptation to the environment. This system shows seasonal changes linked to the environment. The experimental model used in the present study was Lagostomus maximus maximus (viscacha). The reproduction of males of this species is photoperiod dependent. Twenty-four adult male viscachas were captured in their habitat at different times during one year. The adrenal glands were processed for light microscopy. Serial cuts were stained with hematoxylin-eosin for the morphometric study, and 100 nuclei of each zone of the adrenal cortex were counted per animal. Data were analyzed statistically by ANOVA and the Tukey test. The cells of the glomerulosa zone are arranged in a tube-shaped structure. The fasciculata zone has large cells with central nuclei and clearly visible nucleoli and with a vacuolar cytoplasm. In the reticularis zone there are two of types of cells, one with a nucleus of fine chromatin and a clearly visible nucleolus and the other with nuclear pycnosis. Morphometric analysis showed maximum nuclear volumes during the February-March period with values of 133 +/- 7.3 microm3 for the glomerulosa, 286.4 +/- 14.72 microm3 for the fasciculata, and 126.3 +/- 9.49 microm3 for the reticularis. Minimum nuclear volumes were observed in August with values of 88.24 +/- 9.9 microm3 for the glomerulosa, 163.7 +/- 7.78 microm3 for the fasciculata and 64.58 +/- 4.53 microm3 for the reticularis. The short winter photoperiod to which viscacha is subjected could inhibit the adrenal cortex through a melatonin increase which reduces the nuclear volume as well as the cellular activity.

Electron microscopic studies on the pineal organ of the antarctic penguin, (Pygoscelis papua).

The pineal organ of the migratory antarctic penguin, Pygoscelis papua, has a lobular structure. Clusters formed by different types of parenchymal cells are separated by connective tissue septa containing blood vessels. The predominant cell type displays a well-developed Golgi complex, free ribosomes, clear and granular vesicles (secretory granules), and lysosomes. Other cell types found in the gland are supporting and ependymal-like cells. The former contain dense bodies and filament bundles, the latter possess abundant cilia and clusters of ribosomes. Typical photoreceptor elements are lacking. Blood vessels are located within a perivascular space bordered by basal laminae. This perivascular space extends between the basal protrusions of the parenchymal cells. The presence of pinocytotic vesicles, secretory granules and cytoplasmic processes in the vicinity of these spaces suggests active sites of transport and exchange of substances. Intercellular conaliculi-like spaces are surrounded by parenchymal cells rich in microvilli. These cancliculi are continuous with the cavities (invaginations) of secretory and other parenchymal cells.

Effect of dexamethasone on the neonatal adrenal medulla.

Newborn male rats were injected with a single dose of dexamethasone on the first day of life. Controls received only the diluent. Two to ten days later the experimental and control animals were sacrificed, and the adrenal medullae were processed for electron microscopy and for histochemical demonstration of catecholamines. Rats that received dexamethasone, as compared to controls showed (1) an earlier appearance of the catecholamine reactions, and (2) a pronounced development of Golgi complex. These results are further indication that glucocorticoid stimulates the maturation of the chromaffin complex. The Golgi apparatus may play some role in this inductive mechanism.

Effect of dehydroleucodine on mucus production: a quantitative study.

We have demonstrated that dehydroleucodine (DhL), a lactone isolated from Artemisia douglasiana Besser, prevents gastroduodenal damage induced by necrosis-inducing agents such as absolute ethanol. We have also reported, in a qualitative study, that this effect is related to the ability of the drug to stimulate mucus production. The present study was designed to quantitatively evaluate the effect of DhL on adherent mucus layer thickness, to obtain a more objective approach to the mechanism of action of the drug. Mice were divided into two groups: (I) controls were treated with orally administered carboxymethylcellulose (CMC) and (II) experimental animals received DhL in CMC. The thickness of the mucus gel layer was measured in unfixed stomachs and duodena, using an image analysis system. We observed an increase in the adherent mucus layer thickness in the experimental samples. This confirms that one of the main mechanisms involved in the cytoprotective action of the drug is mucus secretion.

Catecholaminergic responses of neonatal adrenal gland to insulin.

In the present work we study a sequential degree of response to insulin (0.001 IU/g body weight) in neonatal rats, using as parameters the blood glucose and the adrenal catecholamine levels. In 1-day and 90-day-old rats treated by insulin the glycemia showed a more marked fall than the rest of neonates. After insulin administration noradrenaline content did not show differences between control and treated rats. In contrast, adrenaline depletion was significant in adults (62.20%) and in neonates of 7 and 10 days of age (45% and 35.5% respectively). No significant decrease of the amine was observed in the younger rats (1 to 4-days-old). This response to insulin probably depends on the gradual maturation and innervation of the adrenal chromaffin tissue.

Unusual cytoplasmic bodies in chromaffin cells of the adrenal medulla of the viscacha (Lagostomus maximus maximus).

Complex structures can be seen associated with large areas of endoplasmic reticulum of the chromaffin cells in the viscacha adrenal medulla. These structures are cylindrical in shape and are formed by chains of globular subunits. A central lumen is observed within which there are bodies resembling chromaffin granules. Parallel cisternae of the endoplasmic reticulum are arranged surrounding these bodies. The functional significance of these structures in unknown.

Effect of insulin on neonatal and adult adrenal medulla in the rat.

The effect of equivalent doses of insulin on the adrenal of both adult and neonatal rats was compared. Glycemia in treated adults dropped to one third of the control, in contrast to the neonatal rat values, which decreased to about one half. After insulin, a large percentage of adult chromaffin cells showed cytoplasmic degranulation and vacuolization. In contrast, a smaller percentage of cytoplasmic changes was seen in the adrenal cells of 4- and 7-day-old rats. In rats of 10 days of age, the percentage of modified cells was similar to the adults. The morphological changes in neonatal medullae were characterized by widening of the perigranular space and enlargement of the endoplasmic reticulum cisternae. No cytoplasmic vacuolization was seen. This response of neonatal rats to insulin may indicate immaturity of the adrenal chromaffin tissue and/or of the centers involved in the mechanism of hypoglycemia-catecholamine release.

Adrenal cytochrome-c-oxidase in neonatal and adult rats: sex differences.

Cytochrome-c-oxidase was measured in the adrenals of neonatal rats from 1 to 10 days of age and adult rats. No differences between the adrenals of female and male neonatal rats of the same age were found. Adult rats, on the contrary, showed sexual differences. Enzymatic activity was higher in males than in females. In the latter, there were important changes during the estrus cycle. The highest values were observed during diestrus and the lowest during estrus. These results provide new evidence of the close interrelations between gonads and adrenal glands during sexual maturation.

An ultrastructural stereologic study of mitochondria in the neonatal adrenal cortex of the rat.

The ultrastructural changes observed during the neonatal period of the rat adrenal cortex are described. The zona juxta-medullaris cells presented round mitochondria with vesicular cristae and large endoplasmic reticulum. Variations on the surface of the mitochondrial cristae were determined by morphometric methods. The cortical cells of 1 and 10-days-old rats showed a well developed endoplasmic reticulum. Morphological analysis indicate that the number of mitochondrial cristae increase the third day, followed by a decrease. At the tenth day a second increase was observed. Plasma corticosterone was also measured. The highest levels of this hormone were found in the 1, 2 and 10-days-old rats. A decrease was observed in rats of 3 to 8 days of age. This result is coincident with the adrenal changes observed in the developing of mitochondria and endoplasmic reticulum in the neonatal period. The increase in the number of mitochondrial cristae in the three-days old rats can be considered a morphological expression of the neonatal gland in the period influenced by maternal dependence. The most important morphological and metabolic changes observed the second week of life are probably due to the maturation of the hypothalamic pituitary axis that stimulates the neonatal adrenal cortex secretion, which is independent of maternal dependence.

Colloid in the pituitary pars distalis of viscacha (Lagostomus maximus maximus): ultrastructure and occurrence in relation to season, sex, and growth.

Randomly distributed extracellular colloidal accumulations were observed in the pars distalis of viscacha (Lagostomus maximus maximus). They were preferentially located in the peripheral zone of the gland and showed variability in shape and size. Two different types of colloidal accumulations were found by electron microscopy: 1) those surrounded by nongranulated follicular cells that correspond to characteristic follicles, and 2) those surrounded by granulated cells. In the follicles lined by nongranulated follicular cells, long, prominent microvilli and cytoplasmic processes protruded into the lumen. The frequency of these accumulations varies during the year in adult male animals, showing an increase in number during summer and a decrease during winter. The lowest value was registered in August (winter). The mean follicular diameter did not vary seasonally. The number of colloidal accumulations did not vary seasonally in adult female viscachas, but a significant difference in the mean follicular diameter between pregnant and non-pregnant females was observed. Pituitaries of immature animals contain fewer colloidal accumulations than those of adults. In fetuses, these accumulations were absent. The administration of melatonin provoked a decrease in the number of these structures. The numeric changes of the colloidal accumulations observed in this study are associated with: 1) the seasonal reproductive activity in adult males, and 2) the reproductive condition, body weight and sexual maturity in males and females. The fact that melatonin administration decreases the population of colloidal accumulations in males suggests participation of the pineal gland in these changes.

Biological role of the pineal. Responses to the environmental photoperiod.

The pineal of vizcacha (Lagostomus maximus maximus) in specimens collected during winter, has the cytological characteristic of an active organ. In this state the animal is adapted to a prolonged dark environment and its reproductive organs are inactive. During summer, the vizcacha displays its sexual annual cycle of reproduction and the pineal is apparently inactive. These seasonal pineal changes may be related to the natural photoperiod and the gradual exposure to twilight during the long daylight summer period. This photic information may be expressed as changes in the sympathetic tone of the pineal. The vizcacha and rat's pineals may also influence on the pituitary pars intermedia secretion to respond as photoreceptors in the mechanism of adaptation to the natural photoperiod.