Morphological study of changes in the baboon oviductal epithelium during the menstrual cycle

Advances in understanding mechanisms of long-term sperm storage-the soft-shelled turtle model

Long-term sperm storage is a special reproductive strategy, which can extend the time window between mating and fertilization in some animal species. Spermatozoa of the soft-shelled turtle, Pelodiscus sinensis, can be stored in the epididymis and oviduct for at least six months and one year, respectively. How spermatozoa can be stored in vivo for such a prolonged period is yet to be explained. We analyze the mechanisms that contribute to long-term sperm storage in P. sinensis, and compare them with other species from three different perspectives: the spermatozoon itself, the storage microenvironment and the interaction between the spermatozoon and microenvironment. Characteristics of soft-shelled turtle spermatozoa itself, such as the huge cytoplasmic droplet with its content of several large lipid droplets (LDs) and onion-like mitochondira, facilitate long-term sperm storage. The microenvironment of reproductive tract, involving in the secretions, structural barriers, exosomes, androgen receptors, Toll-like receptors and survival factor Bcl-2, are important for the maintenance of spermatozoa long-term storage. Sperm heads are always embedded among the oviductal cilia and even intercalate into the apical hollowness of the ciliated cells, indicating that the ciliated cells support the stored spermatozoa. RNA seq is firstly used to detect the molecular mechanism of sperm storage, which shows that autophagy, apoptosis and immune take part in the long-term sperm storage in this species.

Novel cellular evidence of oviduct secretions in the Chinese soft-shelled turtle Pelodiscus sinensis

The oviduct is the location of fertilization and sperm storage. We examined the ultrastructure of the oviduct epithelium and its glandular secretions in the isthmus, uterus and vagina of Chinese soft-shelled turtle Pelodiscus sinensis using light and transmission electron microscopy. The epithelium in these segments is lined with ciliated, secretory and other cells; the first two cell types span the entire epithelium, with secretory cells being predominant. The ciliated cells are characterized by the presence of a secretory vacuole that releases apocrine secretions into the lumen, whereas the secretory cells contain typical biphasic granules with both dark and light aspects. The third type of cells observed have wider proximal portion, abundant mitochondria, vacuoles, and narrow nuclei. The storage of spermatozoa is restricted to the isthmus, uterus, and vagina. In addition, the gland cells show prominent features, including the presence of granules of different shapes, sizes, and electron densities. The synthesis of these granules is described for the first time in this study. Mitochondria appear to play an important role in the formation of dense granules, the rough endoplasmic reticulum and microfilaments may also play a role in the maturation of these dense granules. After completing the maturation process, these granules are released into the lumen of the gland cells.

Morphometric and ultrastructural features of the mare oviduct epithelium during oestrus

Morphometric, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations have displayed regional differences in the mare oviductal epithelium. The entire mucosa of the oviduct was lined with a pseudostratified epithelium, which consisted of two distinct cell types, ciliated and non-ciliated. Ciliated cells were predominant in the three different segments of the oviduct and their percentage increased from fimbriae to ampulla and significantly decreased in the isthmus. SEM revealed in the infundibulum finger-like mucosal folds, some of them interconnected, in the ampulla numerous and elaborated branched folds of the mucosa, whereas the isthmus displayed a narrow lumen, short and non-branched mucosal folds. In the ampulla and isthmus the majority of non-ciliated cells showed apical blebs provided or not of short microvilli. TEM displayed different ultrastructural features of ciliated and non-ciliated cells along the oviduct. Isthmus ciliated cells presented a more electron-dense cytoplasm than in infundibulum and ampulla cells and its cilia were enclosed in an amorphous matrix. The non-ciliated cells of infundibulum did not contain secretory granules but some apical endocytic vesicles and microvilli coated by a well developed glycocalyx. Non-ciliated cells of ampulla and isthmus contained secretory granules. Apical protrusions of ampulla displayed two types of secretory granules as well as occasional electron-lucent vesicles. Isthmus non-ciliated cells showed either electron-lucent or electron-dense cytoplasm and not all contained apical protrusions. The electron-dense non-ciliated cells displayed microvilli coated with a well developed glycocalyx. Three types of granules were observed in the isthmus non-ciliated cells. The regional differences observed along the epithelium lining the mare oviduct suggest that the epithelium of the each segment is involved in the production of a distinctive microenvironment with a unique biochemical milieu related to its functional role.

Prenatal Development of the Bovine Oviduct

In this study the development of the bovine Fallopian tube was investigated using light microscopic methods. Formation and differentiation of the Müllerian duct were studied in mesonephroi of 16 embryos and fetuses with a crown-rump lengths (CRL) of 0.9-8.4 cm. The funnel field, the rostral beginning of the Müllerian duct was first observed at a CRL of 0.9 cm. It appears as a thickening of the mesothelium on the craniolateral side of the mesonephros. During later development the Müllerian duct emerges by caudal outgrowth from the funnel field. Formation of a common basal lamina surrounding the caudal tips of Müllerian and Wolffian ducts could be observed at all stages up to CRL of 2.7 cm. The mesothelium and the epithelium of the Wolffian duct adjacent to the Müllerian duct showed a modification of epithelium height in all examined stages. Probably the Wolffian duct influences the growth of Müllerian duct by epithelio-mesenchymal interactions. Fetuses from a CRL of 12.0 to 94.0 cm were used for investigation of the prenatal differentiation of the oviductal mucosa. Folding of the oviductal mucosa started at a CRL of 29.0 cm and continued until birth. Individual primary, secondary and tertiary folds are formed in special proliferation zones and epithelium-folding buds. The cellular differentiation of the oviductal epithelium involves the formation of ciliated and secretory cells during different times of prenatal development. Ciliogenesis was first detected at a CRL of 33.0 cm. Active secretory cells could be observed in the oviductal epithelium from a CRL of 64.0 cm onwards.