The present study describes in detail the morphological characteristics of the process of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season using light and electron microscopy and immunohistochemistry. The follicular regression process was initiated with shrinkage and disintegration of the nuclear membrane of oocytes resulting in dispersing of chromatin within the ooplasm, followed by marked hyperplasia and hypertrophy of follicular and granulosa cells, which exhibited a strong phagocytic activity to engulf the liquefied yolk particles. Rodlet cells and granulocytes were recorded on the follicular wall and invaded the regressed follicles. Rodlet cells expressed a strong immunoreactivity to matrix metalloperoxidase (MMP-9) and α-smooth muscle actin, while neutrophils expressed a strong reactivity to Myeloperoxidase-3 (MPO). In the advanced stage of follicular atresia, the yolk was almost phagocytized and resorbed and the regressed follicle lost its integrity and appeared to be formed of a cellular mass of phagocytic cells. Transmission electron microscopy revealed the presence of neutrophils, eosinophils, and dendritic cells within the atretic follicle in between these phagocytic cells. Moreover, numerous lysosomes, granules, and phagosomes were observed within the cytoplasm of both phagocytic cells and granulocytes. Telocytes were also demonstrated within the highly thickened richly vascularized theca layer during the late stages of follicular atresia. Immunohistochemical staining for caspase-3 established the participation of apoptosis in the advanced stages of follicular regression. Immune cells, rodlet cells, and telocytes in combination with follicular cells play an essential role in follicular atresia. In conclusion, the present study provides a new evidence on the role of both somatic and immune cells in the phenomenon of ovarian follicular atresia in Redbelly tilapia (Coptodon zillii) during the nonbreeding season.

中文翻译：

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鱼类卵巢滤泡闭锁的显微分析：体细胞和免疫细胞可能的协同作用

本研究详细描述了红腹罗非鱼卵巢滤泡闭锁过程的形态特征。紫菜) 在非繁殖季节使用光学和电子显微镜以及免疫组织化学。卵泡退化过程始于卵母细胞核膜的收缩和解体，导致染色质在卵质内分散，随后卵泡和颗粒细胞明显增生和肥大，表现出强烈的吞噬作用，吞噬液化的蛋黄颗粒。在滤泡壁上记录了棒状细胞和粒细胞并侵入退化的滤泡。Rodlet 细胞对基质金属过氧化物酶 (MMP-9) 和 α-平滑肌肌动蛋白表达了强烈的免疫反应性，而中性粒细胞对髓过氧化物酶-3 (MPO) 表达了强烈的反应性。在滤泡闭锁的晚期，蛋黄几乎被吞噬和吸收，退化的卵泡失去了完整性，似乎由吞噬细胞的细胞团形成。透射电子显微镜显示在这些吞噬细胞之间的闭锁滤泡内存在嗜中性粒细胞、嗜酸性粒细胞和树突状细胞。此外，在吞噬细胞和粒细胞的细胞质中观察到大量溶酶体、颗粒和吞噬体。在滤泡闭锁的晚期阶段，在高度增厚的富含血管的膜层中也显示了特洛细胞。caspase-3 的免疫组织化学染色确定细胞凋亡参与了卵泡退化的晚期阶段。免疫细胞、棒状细胞和端粒细胞与滤泡细胞结合在滤泡闭锁中起重要作用。紫菜) 在非繁殖季节。