Gonadal development of quail embryos was examined histologically using histological and histochemical methods. In the present study, quail embryos were studied at various stages of incubation period based on phases of gonadogenesis. Germ cell migration was observed on day 3-4 but gonadal differentiation and gonadal function were observed on day 6–8 and day 11–14, respectively. During germ cell migration, quail primordial germ cells (qPGCs) were successfully detected in both left and right genital ridges as well as the dorsal mesentery by lectin histochemistry. Unexpectedly, qPGCs-like cells were found next to the neural tube by Mallory-AZAN stain. During gonadal differentiation, embryonic sex can be distinguished histologically since day 8 of incubation. Embryonic testis exhibited a thin cortex, whereas embryonic ovary exhibited a thick cortex. Testicular cord formation was found in the medulla of embryonic testes while the lacunae and fat-laden cells were found in the medulla of embryonic ovary during gonadal function. This is the first report on a comparison of phases of gonadogenesis and histochemical study of quail embryonic gonads in both sexes.
Genistein (GEN), an isoflavonoid phytoestrogen, is one of the potent estrogenic compounds derived from plants that can cause disrupting effects on sex organ development in non-mammalian and mammalian species. The present study revealed effect of genistein on germ cell number in the genital ridges during gonadogenesis. Genistein (16 and 24 μg/g egg) was injected into the egg yolk prior to incubation. Effect of genistein on quail-primordial germ cells (PGCs) number was examined by counting the number of Wisteria floribunda (WFA)-positive cells localized in both left and right genital ridges compared with the control group. Both concentrations of genistein resulted in significant decrease of PGC number compared with the control group. Percentages of the sterility rate of the embryo treated with 16 and 24 μg of genistein/g egg were 19% and 23%, respectively. These results provide evidence that genistein may be a germ cell toxicant causing sterility later in life of adult birds. This is the first report on the effect of genistein on PGC number in the genital ridges of the avian embryo.
INTARAPAT, S.; SAILASUTA, A. & SATAYALAI, O.Immunohistochemical localization of estrogen receptor in the embryonic gonad of male quail embryo during gonadal differentiation. Int. J. Morphol., 34(2):575-579, 2016.
SUMMARY:In birds, male embryo the gonads develop bilateral testes, in which both left and right sides produce functional spermatozoa, whereas female embryo, only the left gonad develops into a functional ovary. Estrogen plays a key role in avian sex determination in both sexes by binding to the estrogen receptor (ER). Surprisingly, chicken estrogen receptor (cER) mRNA is expressed in both sexes; moreover; its expression is only expressed in the left male gonad. The present study aimed to localize ER protein in the left gonad of male quail embryo using immunohistochemistry. The 8-day-old male quail embryos whose embryonic sex distinguished by gonadal morphology were studied. Histology of the left male gonad displayed thin cortex containing 1 to 2 layers of the germinal epithelium, while testicular cords were observed in the medulla. ER-immunoreactive cells were only found in the germinal epithelium but not in the medulla. Localization of ER was detected in the nucleus and cytoplasm of the germinal epithelial cells. The number of ER-immunoreactive cells counted in upper, lateral, and lower regions of the germinal epithelium was 18.20±1.892, 17.60±1.887, and 16.20±1.290, respectively. This study shows the first evidence for expression of ER protein in the left male gonad of the avian embryo, indicating that ER plays a role in avian gonadal sex differentiation.
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