The development of adrenal homolog of rainbow trout Oncorhynchus mykiss: an immunohistochemical and ultrastructural study

In this work we describe the adrenal homolog of the rainbow trout Oncorhynchus mykiss during development. At the histological level, the interrenal primordium is clearly evident in larvae 25 days after fertilization (dpf), and the immunohistochemical reactions for tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT), which mark the chromaffin cells, appear as early as 27 dpf. Both reactions are evident in cells localized in the head kidney and in some, probably migrating, cells close to the notochord. In 27-dpf larvae, the ultrastructural analysis shows the presence of the interrenal cells with mitochondria with tubulovesicular cristae, typical of steroidogenic cells, sometimes surrounded by smooth endoplasmic reticulum (SER) cisternae, indicating that in this stage the cells have the capacity for steroid synthesis and secretion. In the same stage the chromaffin cells are characterized by few and small membrane-bound granules containing cores of heterogeneous electron density. Both types of cells show large nuclei, numerous free or clumped ribosomes, developed rough endoplasmic reticulum (RER), and scarce SER. Rare nerve endings contacting chromaffin cells are present. In the subsequent developmental stages, a further differentiation of both types of cells is evidenced by modifications of cell organelles as mitochondria, chromaffin granules, RER, SER, and so on. A clear discrimination of the two types of catecholamine-containing cells, adrenaline and noradrenaline cells, is evident only 5 days after hatching. The presence of different interrenal cell types in larvae at 5 and 10 days after hatching probably indicates the activation of a physiological cellular cycle. The immunohistochemical and ultrastructural results are compared with those obtained by other authors in the same and other vertebrate species

Degeneration and possible renewal processes related to the interrenal cells in the head kidney of the stickleback Gasterosteus aculeatus

The ultrastructural aspect of degeneration and recovery processes involving the steroidogenic interrenal cells of the stickleback was studied. Together with the adrenergic cells, the interrenals constitute the adrenal homolog in teleosts. From our study it appears that a process of massive cell death may lead to temporary disappearance of the gland. Moreover, our E.M. observations suggest two main ways, each leading to morphological dedifferentiation of the cells, no longer recognizable as interrenals: the first way involves elimination of organelles and recovery of the nucleus surrounded by a thin rim of cytoplasm; the second involves fragmentation of the cytoplasm by other pyknotic star-shaped interrenals, together with autophagocytosis processes. Our E.M. observations also suggest that the subsequent reconstitution of the tissue can occur in two ways. In the first, the interrenals appear mainly to differentiate from mesenchymatic-like electron-light cells, while in the second, the new interrenals appear mainly raising from some macrophagic electron-dense cells. Some data obtained with Mallory's trichrome staining of histological sections, and localization of the enzyme 3P hydroxysteroid dehydrogenase in thin sections, support the above-mentioned results. A hypothesis is advanced on the origin of the electron-dense differentiating interrenals, and a possible role of dedifferentiated cells in restoration of the interrenal gland is also discussed. (C) 2007 Elsevier Ltd. All rights reserved

Immunohistochemical Localization of Oestrogen Receptor Alpha in the Various Cell Categories of Chick Embryo Ovary

Summary: The immunohistochemical (IHC) localization of oestrogen receptor alpha (ERα) was studied in the developing left ovary of 14.5-day-old chick embryos. The study was focused in particular on distinguishing in cortex and medulla the different cell categories that proved positive to the reaction, in order to gain further understanding of gonadal cell interactions during ovarian development. Immunostained cells were observed in both the cortex and medulla, but the reactivity for ERα was discontinuous, probably due to variable cell requirements. In the cortex, positivity was observed in cells of the ovarian surface epithelium, in germ cells and in prefollicular cells. In the medulla, positivity was found in the following cell categories: interstitial cells, poorly differentiated somatic cord cells, including those delimiting lacunae, germ cells and their accompanying cells of epithelial origin. Furthermore, the IHC results showed that the intracellular localization of the antigen was cytoplasmic, nuclear, or both. The significance of ERα presence and intracellular localization was discussed in relation and as supplementary to previous research by various Authors. In particular, as regards the unusual cytoplasmic immunoreactivity, a gradual shift of ERα localization from cytoplasmic to nuclear during the embryonic period is suggested. © 2010 Blackwell Verlag GmbH