The effects of treatment with melatonin on the ultrastructure of mouse leydig cells: a quantitative study

Both the presence of receptors for gonadal steroids in the pineal gland and in vitro observations of direct action of melatonin upon Leydig cells, inhibiting testosterone secretion, indicate a direct connection between pineal gland and gonadal function. In the present study, we used a transmission electron microscope to analyze the morphologic parameters of Leydig cells from adult Swiss outbred white mice treated with daily subcutaneous injections of 100 µg of melatonin (N-acetyl, 5-methoxytryptamine), during 22 consecutive days, compared with sham-control animals which had only received the melatonin vehicle. The melatonin group of mice showed a decrease in nuclear volume and fractional nuclear volume; smooth and rough endoplasmic reticulum; mitochondria; and Golgi complex. Our data also showed an increase in cytoplasmic volume, fractional cytoplasmic volume, and lysosomes in these same animals. The results suggest that melatonin, directly or indirectly, alters the ultrastructure of mouse Leydig cells and possibly influences their secretory activity by inhibiting their capacity to secrete steroids

The effects of treatment with melatonin on the ultrastructure of mouse Leydig cells: a quantitative study.

Both the presence of receptors for gonadal steroids in the pineal gland and in vitro observations of direct action of melatonin upon Leydig cells, inhibiting testosterone secretion, indicate a direct connection between pineal gland and gonadal function. In the present study, we used a transmission electron microscope to analyze the morphologic parameters of Leydig cells from adult Swiss outbred white mice treated with daily subcutaneous injections of 100 micrograms of melatonin (N-acetyl, 5-methoxytryptamine), during 22 consecutive days, compared with sham-control animals which had only received the melatonin vehicle. The melatonin group of mice showed a decrease in nuclear volume and fractional nuclear volume; smooth and rough endoplasmic reticulum; mitochondria; and Golgi complex. Our data also showed an increase in cytoplasmic volume, fractional cytoplasmic volume, and lysosomes in these same animals. The results suggest that melatonin, directly or indirectly, alters the ultrastructure of mouse Leydig cells and possibly influences their secretory activity by inhibiting their capacity to secrete steroids.

The effect of treatment with melatonin upon the ultrastructure of the mouse pineal gland: a quantitative study

In order to evaluate melatonin implication in the regulating of its own secretory process by pinealocytes, we used morphometric techniques for transmission electron microscopy. In mice treated with 100 mg of melatonin (N-acetyl-5-methoxy-tryptamine) by daily subcutaneous injection, we observed a decrease in number and volumetric density of lysosomes. Our results showed that melatonin influences the secretory activity of pinealocytes and participates in a complex secretory regulating mechanism

The effect of treatment with melatonin upon the ultrastructure of the mouse pineal gland: a quantitative study.

In order to evaluate melatonin implication in the regulating of its own secretory process by pinealocytes, we used morphometric techniques for transmission electron microscopy. In mice treated with 100 mg of melatonin (N-acetyl-5-methoxy-tryptamine) by daily subcutaneous injection, we observed a decrease in number and volumetric density of lysosomes. Our results showed that melatonin influences the secretory activity of pinealocytes and participates in a complex secretory regulating mechanism.

The effects of testosterone on the mice pinealocytes: a quantitative study.

In order to determine the effects of testosterone upon the function of the pineal gland we quantitated, under the electron microscope, the number of dense-core vesicles, lysosomes, lipid droplets and the fractional volume of the pineal gland components in adult male mice. We studied six groups of mice submitted to different treatments as follows: treated with testosterone propionate (0.1 mg/10 g body weight for 15 consecutive days), castrated and the respective control mice. In mice treated with testosterone we observed a decrease in the number and fractional volume of dense-core vesicles and an increase in the fractional volume of lysosomes and lipid droplets. In castrated mice, without treatment, we observed a decrease in the number of lysosomes and an increase in the number and fractional volume of dense-core vesicles. These results show that testosterone is closely related to the secretory process of mice pinealocytes, playing an inhibitory role upon the functional activity of the pineal gland.

[Morphological study of the pineal organ in the spined rat Proechimys iheringi Thomas, 1911]. / Estudo morfológico do órgáo pineal do rato-espinho Proechimys iheringi Thomas, 1911.

The pineal organ of the spined rat is located deeply near the third ventricle. The organ shows a compact pattern of organization with pinealocytes and astrocytes arranged in cords and rosettes. Numerous concretions positive to chrome alum hematoxylin technic are visualized in the adjacent tissue near the pineal organ and in the vicinity of the veins which drain the blood of the organ. In the present work we discuss the probable origin of these concretions.

[Histologic study of the pineal organ in tinamid birds]. / Estudo histológico do órgão pineal em aves tinamiformes.

The pineal organs of 10 species of tinamid birds belonging to the genera Crypturellus, Nothura, Rhynchotus and Tinamus were studied in serial microscopic sections of the entire medial region of the brain. All were located in a triangular space formed by the cerebral hemispheres and the cerebellum. They have the form of a club with the enlarged distal part enclosed in the dura-mater. In all species the pineal is formed of tubulofollicular structures, the walls of which are covered by a pseudo-stratified epithelium with elongated cells. In Rhynchotus and Nothura there is a predominance of small follicles with a reduced lumen and a regular outline, whereas in Tinamus and Crypturellus there is a predominance of large follicles with a wide lumen and an irregular outline. Our results show that morphological organization of the pineal organs in tinamids is similar to that observed for the majority of modern birds, in spite of the fact that they are generally regarded as very primitive.

Annulate lamellae in the pineal organ of a tinamid bird.

This study reports the occurrence of annulate lamellae in the rudimentary photoreceptor cells of the pineal organ of a tinamid bird Crypturellus parvirostris. The annulate lamellae observed in these cells are located in the cell body and are comprised of 1 to 8 parallel lamellae, symmetrically aligned and regularly spaced. Each lamella consists of pairs of parallel membranes interrupted by regularly spaced pores or annuli. These observations are discussed and compared with the structure and distribution of these organelles referred in the literature.

Submicroscopic study of the tunica propria of the seminiferous tubules of the Brazilian white-belly opossum (Didelphis albiventris).

The components of the white-belly testicular tunica propria are the same as observed in the testis of eutherian mammals, i.e., basal lamina, collagen fibrils, oxytalan and elaunin fibers, myoid cells and fibroblasts. The main structural difference between the tunica propria in white-belly opossum (methatheria) and other mammals is the presence of fibroblasts internally located to the myoid cells in the white-belly opossum tunica propria.

Ultra-estrutura do orgao pineal do Crypturellus parvirostris Wagler 1897 (Aves. Tinamiformes). / Ultrastructure of the pineal organ of Crypturellus parvirostris Wagler, 1897 (Aves. Tinamiformes)

Estudou-se a ultra-estrutura do orgao pineal da ave Tinamiforme Crypturellus parvirostris. Ele apresenta uma organizacao folicular com celulas do tipo fotoreceptor rudimentar (celula A) e celulas de sustentacao (celulas B). As primeiras possuem morfologia de celulas fotoreceptoras, com excecao do pediculo basal, que e assinaptico, e do segmento externo, que e atipico e esta representado por um cilio dilatado do tipo 9 + 0 (bulbo-cilio). Assim, apesar do Crypturelus parvirostris pertencer a um grupo de aves considerado muito primitivo, sua pineal nao apresenta caracteristicas morfologicas que indiquem uma atividade fotossensorial pelo menos do tipo convencional. Entretanto, a presenca de um complexo de Golgi bem desenvolvido de cisternas do reticulo endoplasmatico granular muito dilatadas e de abundantes vesiculas indicam a existencia de uma atividade secretora intensa. A presenca de vesiculas revestidas em relacao com a membrana dos processos apicais sugere uma interacao entre estes processos e a substancia na luz dos foliculos