This study sought to examine the ovarian cellular and stromal components of the zebrafish (Danio rerio) throughout the spawning season using light and electron microscopic tools. The ovaries of zebrafish showed oocytes in all stages of follicular development and degeneration (atresia). Six stages of oogenesis were demonstrated: oogonia, early oocytes, late oocytes, vacuolated follicles, the yolk globule stage (vitellogenesis), and mature follicles. The SOX9 protein was expressed in the ooplasm of the primary and previtellogenic oocytes and the theca cell layer of the mature follicles. Myostatin was expressed in the granulosa and theca cells. Many stem cells in the ovarian stroma expressed myostatin and SOX9. During the spawning season, the EM results indicated that the zona radiata increased in thickness and was crossed perpendicularly by pore canals that contained processes from both oocytes and zona granulosa. The granulosa cells contained many mitochondria, rER, sER, and vesicles. Meanwhile, the thecal layer consisted of fibroblast-like cells. Atretic follicles could be demonstrated that involved both oocytes and their follicular walls. Several types of cells were distinguished in the ovarian stroma, including mast cells, telocytes, lymphocytes, fibroblasts, endocrine cells, macrophages, adipocytes, dendritic cells, and steroidogenic (stromal) cells. The ovary of the zebrafish serves as a model to investigate follicular development.

Identifying and locating stem cell populations in the limbus may lead to developing a cell-based strategy for treating the corneal injury. Therefore, this study was the first to design a follow-up on the microscopical and histomorphometric changes in the rabbit limbus and to localize and demonstrate the limbal stem cell niche during postnatal development. The paraffin sections from the eyes of different postnatal-developmental stages were stained and examined using light microscopy. Furthermore, sections were immunohistologically stained for the epithelial stem cell differentiation marker, cytokeratin-14. Moreover, semithin and ultrathin sections were applied for ultrastructural demonstration of the stem cell niche. This study revealed that the number and thickness of limbal epithelial layers increased with age, whereas the thickness of limbal stroma decreased. Additionally, the immunohistochemical data showed that ck14 staining intensity increased in the limbal region where limbal stem cells reside. The semithin and ultrastructure investigation revealed stem cell clusters within the limbus’s underlying stroma close to the blood and nerve supply and surrounded by telocytes. Conclusively, isolated clusters of limbal epithelial stem cells combined with blood vessels, nerve fibers, and telocytes propose a harmonious microenvironment of a stem cell niche.

The molly fish is a member of viviparous teleosts that are characterized by the fusion of the right and left ovaries during their early embryonic development. This fusion results in a singular and saccular ovary, where the germinal epithelium lines the internal lumen. The present study aimed to identify the immune cells in the ovarian stroma of Molly fish during the breeding season using histological and immunohistochemical analysis. Histological examination of the ovaries displayed oocytes at all different stages of development and degeneration. The ovocoel, a lymph-filled space, remains in the center of the ovary and branches posteriorly, creating the lumen of the gonoduct. The ovarian wall is composed of three layers: the mesothelium, tunica albuginea, and germinal epithelium. The developing ova were held together by the stroma, which consisted of vascular collagenous connective tissue clustered with immune cells. Immunohistochemical analysis revealed the presence of clusters of macrophages expressing APG5, IL-1β, TGF-β, S100, NF-κB, CD68, Iba-1, and Ach. Monocytes demonstrated positive immunoreactivity for both APG5 and IL-1β, whereas dendritic cells expressed only APG5. Furthermore, rodlet cells exhibited immunoreactivity for S100 protein, IL-1β, NF-κB, CD68, Nrf2, Ach, myostatin, SOX9, and Iba-1. In contrast, stem cells displayed immunoreactivity for Nrf2, myostatin, and SOX9. In conclusion, the ovarian stroma of Molly fish demonstrated a notable presence of immune cells, indicating their active involvement in immune reactions.

Studying scute and fin morphology are advantageous approaches for phylogenetic identification and provide information on biological linkages and evolutionary history that are essential for deciphering the fossil record. Despite this, no prior research has precisely characterized the histological structures of scutes in the common pleco. Therefore, this research investigated the microstructure and organization of bone tissue within the dermal skeleton, including the scutes and fins, in the common pleco, using light microscopy, stereomicroscopy, and scanning electron microscopy. The dermal scutes were organized in a pentagonal shape with denticular coverage and were obliquely aligned with the caudal portion pointing dorsally. The dermal scutes consisted of three distinct portions: the central, preterminal, and terminal portions. Each portion comprised three layers: a superficial bony plate, a basal bony plate, and a mid-plate. Both the superficial and basal bony plates were composed of lamellar bone and lamellar zonal bone, whilst the mid-plate consisted of secondary osteons and woven bone. In the terminal portion, the superficial and basal bony plates became thinner. The pectoral fin consists of spines and rays composed of lepidotrichium (two symmetrical hemi-rays). The spine contained centrifugal and centripetal lamellar and trabecular bones. A centripetal fibrous bone was implanted between the lamellar bones. Besides being oriented in a V shape, the hemi-rays were also composed of thin centrifugal and centripetal lamellar bones and trabecular bones. A fibrous bone was identified between the centrifugal and centripetal bones. The trabecular bone and lamellar bone were made up of bone spicules.

Rabbits have been proposed as a model for the human meibomian gland (MG), a large specific sebaceous gland in the eyelid that consists of secretory acini arranged laterally and related to the central duct via short ductules, with the central duct continuing as an excretory duct to open at the free margin of the lid. First detected at embryonic day 18 as an aggregation of mesenchymal cells in the tarsal plate, it completes its development approximately 2 weeks postnatal when the separation of the eyelids is completed. The Transmission electron microscopy supports the meibocytes’ gradient maturation to the meibum’s synthesis. While the differentiating cells, their cytoplasm, are well packed with lipid droplets, the basal cells are characterized by a high nuclear to cytoplasm ratio. The androgen and estrogen receptor proteins are expressed in the basal cell and the meibocytes, and increase in age increases in the expression of these proteins. Additionally, the cytokeratin (CK14) is expressed in the basal and differentiating cells of the acini and the ductal epithelium. Therefore, the duct cells of the MG are common in all stem cells. These data concluded that the MG plays a major role in maintaining the health of the ocular surface and preservation of visual acuity. Any abnormalities in the structure of the MG lead to its dysfunction and changes in lipid secretion.

Japanese quails are an important source of animal protein. Several recent researches aimed to add natural supplements to the quails’ ration to enhance growth, food conversion, or reproductivity. However, the possible adverse effects are almost neglected. This study aims to highlight the effects of Ginger roots on the histological features and functional parameters of the liver and kidney in Japanese male quails. Birds were divided randomly into three equal experimental groups. The first group (control group) was fed a commercial basal mash ration, while the second and third groups were fed on the same ration mixed with 10 and 15 grams of ginger roots/Kg feed, respectively. Supplementation with both doses of Ginger resulted in histopathological abnormalities in the liver and kidney. However, the hepatic and renal cytological deteriorations were mild to a moderate degree. Plasma aspartate aminotransferase and alanine transaminase were significantly higher in the low Ginger group than in the high Ginger and control groups. Ginger at both doses induced a significant decrease in plasma total cholesterol and uric acid levels and a significant increase in plasma lipid peroxides in Japanese male quails. Despite the observed hepatic and renal histopathological alterations in the Ginger treated groups, they are not sufficient to cause hepatic and renal dysfunction based. In conclusion, using ginger supplementation in quail could be applied at these doses and duration of intervention, however, with caution because the liver and kidney are sensitive to ginger.