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 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

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