Carbohydrate characterization of quail primordial germ cells during migration and gonadal differentiation

Ultrastructure characteristics of primordial germ cells in stage X of pheasant (Phasianus colchicus) embryo

Stage X is one of the formation stages in birds at which the blastoderm area is distinguished by two areas of area pellucida being responsible for formation of embryonic tissues and primordial germ cells, and area opaca forming the extra-embryonic tissues. Primordial germ cells are multi-potent stem cells giving rise to spermatogonia or oogonia. The present study was carried out to describe the characteristics of primordial germ cells in stage X of pheasants' embryo using a transmission electron microscope. The blastoderm was dissected out from embryos which were already incubated for 12 hr. Toluidine blue was used for staining semi-thin sections; lead citrate and uranyl acetate were also used to stain ultra-thin sections. Images of primordial germ cells elucidated that the nucleus was situated eccentrically and had a compact spherical structure. Moreover, the nucleolus appeared elongated and was located eccentrically. The cytoplasm was composed of yolk granules and glycogen particles. Mitochondria were observed as round structures in the cytoplasm. The most important finding was that the primordial germ cells contained yolk granules, mitochondria and small amount of glycogen at this stage.

Ostrich (Struthio camelus) primordial germ cells in embryonic blood and presumptive gonad: characterization by PAS and immunohistochemistry

BACKGROUND

Among the birds, chicken was the model used in the majority of studies on germ cells and other birds like quail, turkey and pheasant had some interest but ostrich has been lacking from these researches.

AIMS

The present study was conducted to confirm the presence of ostrich primordial germ cells (PGCs) in the embryonic blood and to determine the appropriate time for having them in the blood.

METHODS

Embryos were extracted in embryonic day (E) 6-12, their blood was obtained and the rest of the embryos were processed for histological examinations. Staining by periodic acid-Schiff (PAS) method and immunohistochemistry (IHC) using stage-specific embryonic antigen 1 (SSEA1) and stage-specific embryonic antigen 4 (SSEA4) antibodies (Abs) were used for identification of the PGCs.

RESULTS

While the blood circulating ostrich PGCs were SSEA1-negative and SSEA4-positive, in the presumptive gonads PGCs showed negative immunoreactivity for both Abs. Although the ostrich PGCs were PAS-positive in both blood and presumptive gonad, their PAS-positive contents reduced during development from E 10 to E 12.

CONCLUSION

E 9, when the hind limb buds appear, is the best time for detecting PGCs in the ostrich embryonic blood.

Microanatomical Study of Embryonic Gonadal Development in Japanese Quail (Coturnix japonica)

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.

Sex- and age-related variation in neurosteroidogenic enzyme mRNA levels during quail embryonic development

Brain can synthesize steroids de novo from cholesterol and this biochemical feature is a conserved property of vertebrates. There is growing evidence indicating that neurosteroids might participate in sexual differentiation of the brain. Therefore, in this study we investigated the presence, the sex differences, and the development-dependent variation of mRNAs coding for key neurosteroidogenic enzymes, namely cytochrome P450 side-chain cleavage enzyme (P450scc), 3beta-hydroxysteroid-dehydrogenase/Delta5-Delta4-isomerase (3beta-HSD), cytochrome P450 17alpha-hydroxylase/c17, 20-lyase (P450c17), and aromatase in embryonic prosencephali. Our results indicated that 3beta-HSD mRNA levels were sexually dimorphic and developmental age-dependent. In particular, 3beta-HSD mRNA levels were higher in females than in males at E7, whereas, this dimorphism was reversed at E9 and E15. In females, the relative levels of 3beta-HSD mRNA were highest at E7, whereas, in males they were significantly higher at E9 and E15 than at E7 and at E11. This sexual dimorphism was a peculiar feature of the prosencephalon, it could not be observed before gonadal sexual differentiation and it was not paralleled by a dimorphism in the brain content of progesterone. The level of mRNA coding for P450scc and for P450c17 did not show obvious developmental- or sex-related variation. Aromatase mRNA varied as a function of the embryonic age but not of the sex. These results, taken together, are suggestive of a potential role of some neurosteroidogenic enzymes in the development of quail brain and suggest that sexual differences in the hormonal environment may occur during brain development.