Morphology and immunolocalization of intertubular steroidogenic cell in mesonephros of Podocnemis expansa during gonadal differentiation

Sex steroid hormones are critical in gonadal differentiation in turtles. The gonads are not the only organs responsible for producing these hormones during this phase. Mesonephros play an important role in steroidogenesis. The present study aimed to investigate the presence of steroidogenic cells in mesonephros of Podocnemis expansa during gonadal differentiation and to evaluate their morphology and ultrastructure. Ten embryos of P. expansa were collected from 5 nests on day 36 of incubation, during spawning period on an artificial beach. Embryos were extracted from eggs by slicing the shell and euthanized. They were dissected under a stereoscopic microscope to collect the gonad-mesonephro complex, in which were fixed and subsequently processed for light microscopy, immunohistochemistry and transmission electron microscopy analysis. During histological analysis was observed mesonephros has typical morphological structure. Immunohistochemistry showed immunoreaction to aromatase in cells of intertubular space. Confirming these findings, it was possible to observe a type of intertubular cell in several regions of mesonephro, being more predominant in region close to blood vessels, distal and proximal tubules. In ultrastructural analysis these cells were characterized by having a clear, large, and rounded nucleus with evident nucleolus and cytoplasm rich in electron-dense droplets. This study demonstrated for the first time the presence of cells with morphological, immunohistochemical and ultrastructural characteristics similar to steroid-producing cells in P. expansa mesonephrons, suggesting that this organ may contribute to gonadal differentiation in this species.(AU)

Stereology of spix's yellow-toothed cavy brain (Galea spixii, WAGLER, 1831)

Spix's Yellow-toothed Cavy is a histrichomorphic rodent of the Caviidae family found in South American countries such as Brazil and Bolivia. It is a widely-used species as an experimental model in research in reproductive biology due to morphological and reproductive characteristics, such as the similarity in the placental development of Galea spixii and human species. However, there are no studies on the behavior of this species or on its brain morphology. Considering the lack of information in the literature about the brain and internal structures of Galea spixii, this study aimed to stereologic evaluate the brain as well as the volumetric proportions of the hippocampus and corpus callosum. Therefore, ten healthy animals were used from the Wild Animal Multiplication Center of the Universidade Federal Rural do Semiárido. The brains were measured in terms of external length, height and width, followed by fixation in paraformaldehyde solution 4% and coronary cuts with a thickness of 4mm and the rostral face of each cut was photographed, with the images being analyzed to determine the volumetric proportions of the required areas. There was no statistically significant difference between the means of volume, length, width and height when the right and left hemispheres were compared, and there was also no statistically significant difference between the volume of the corpus callosum and hippocampus in both hemispheres. The brain of Galea spixii is larger when compared to the rodent Rattus norvegicus. Volumetric differences may be responsible for distinct behavioral aspects between these species.

Stereology of spix's yellow-toothed cavy brain (Galea spixii, WAGLER, 1831)

Spix's Yellow-toothed Cavy is a histrichomorphic rodent of the Caviidae family found in South American countries such as Brazil and Bolivia. It is a widely-used species as an experimental model in research in reproductive biology due to morphological and reproductive characteristics, such as the similarity in the placental development of Galea spixii and human species. However, there are no studies on the behavior of this species or on its brain morphology. Considering the lack of information in the literature about the brain and internal structures of Galea spixii, this study aimed to stereologic evaluate the brain as well as the volumetric proportions of the hippocampus and corpus callosum. Therefore, ten healthy animals were used from the Wild Animal Multiplication Center of the Universidade Federal Rural do Semiárido. The brains were measured in terms of external length, height and width, followed by fixation in paraformaldehyde solution 4% and coronary cuts with a thickness of 4mm and the rostral face of each cut was photographed, with the images being analyzed to determine the volumetric proportions of the required areas. There was no statistically significant difference between the means of volume, length, width and height when the right and left hemispheres were compared, and there was also no statistically significant difference between the volume of the corpus callosum and hippocampus in both hemispheres. The brain of Galea spixii is larger when compared to the rodent Rattus norvegicus. Volumetric differences may be responsible for distinct behavioral aspects between these species.(AU)