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Although the role of estrogens in the development and function of tissues in the reproductive and other systems has long been recognized, their relative concentrations in target tissues have received scant attention. In this regard, the significance of local metabolism of estrogens is clearly shown by incubation of tissues with radiolabeled estrogens.

Concentrations of circulating progesterone and oestradiol were measured in 96 free-ranging, female Australian sea lions Neophoca cinerea from Kangaroo Island, South Australia. There was a marked increase in the concentrations of both hormones (progesterone from approximately 12 ng ml⁻¹ to approximately 24 ng ml⁻¹; oestradiol from approximately 1.5 pg ml⁻¹ to approximately 14 pg ml⁻¹) about 3.5 months after the probable date of mating, reaching peak values in the 5 months after parturition. Progesterone concentrations remained at peak concentrations for about 2 months, decreasing at approximately 8 months to concentrations approximating those of the first 3 months after parturition. Oestradiol concentrations decreased, after reaching a peak, to 3–4 pg ml⁻¹ at about 8 months after parturition. The timing of the increase in the concentrations of circulating progesterone and oestradiol provides evidence that the blastocyst reactivates and implants between 3.5 and 5 months of pregnancy in Australian sea lions, indicating an embryonic diapause of similar duration to that of other pinnipeds. This would suggest a prolonged postimplantation period of up to 14 months (to fit with the gestation period of 18 months reported for this species) the longest postimplantation period recorded for pregnancy in any pinniped.

Estrogen production by the trophoblast is considered important in early equine pregnancy and leads to high concentrations in yolk-sac (Y-S) fluid. The embryo proper is a potential site for their action. We examined estrogen metabolism in the embryo proper because some actions of estrogens are derived from locally formed metabolites. The embryo proper, as well as separated extraembryonic tissues, of conceptuses collected about day 25 of pregnancy, were incubated with ³[H]-estrone (E₁) and ³[H]-estradiol (E₂). Steroids were recovered from media by solid-phase extraction and eluted separately as unconjugated and conjugated fractions. Profiles of free and sulfo-conjugated fractions were obtained by HPLC. Some differences and similarities were noted for the embryo proper as compared to the extraembryonic tissues. No reduction of E₁ to E₂ was noted for the embryo proper and allantois, but some was seen with the bilaminar Y-S wall. Less conversion of E₂ to E₁ occurred in the embryo proper than in the extraembryonic tissues. Profiles for hydrolyzed sulfates from incubation of the embryo proper were very similar for both substrates, mainly with E₁ present. Thus, low levels of reductase and high levels of oxido- activities were apparent for the 17β-hydroxysteroid dehydrogenase enzymes. Further evidence of an active role for the embryo proper was seen as minor, polar products, and an unknown compound eluting between E₂ and E₁. These findings show, for the first time, that the embryo proper can metabolize estrogens that are found in Y-S fluid – a function of potential significance at this stage in its development.

The bovine was used to examine the potential for WNT signaling to affect the preimplantation embryo. Expression of seven key genes involved in canonical WNT signaling declined to a nadir at the morula or blastocyst stage. Expression of 80 genes associated with WNT signaling in the morula and inner cell mass (ICM) and trophectoderm (TE) of the blastocyst was also evaluated. Many genes associated with WNT signaling were characterized by low transcript abundance. Seven genes were different between ICM and TE, and all of them were overexpressed in TE as compared to ICM, including WNT6, FZD1, FZD7, LRP6, PORCN, APC and SFRP1. Immunoreactive CTNNB1 was localized primarily to the plasma membrane at all stages examined from the 2-cell to blastocyst stages of development. Strikingly, neither CTNNB1 nor non-phospho (i.e., active) CTNNB1 was observed in the nucleus of blastomeres at any stage of development even after the addition of WNT activators to culture. In contrast, CTNNB1 associated with the plasma membrane was increased by activators of WNT signaling. The planar cell polarity pathway (PCP) could be activated in the embryo as indicated by an experiment demonstrating an increase in phospho-JNK in the nucleus of blastocysts treated with the non-canonical WNT11. Furthermore, WNT11 improved development to the blastocyst stage. In conclusion, canonical WNT signaling is attenuated in the preimplantation bovine embryo but WNT can activate the PCP component JNK. Thus, regulation of embryonic development by WNT is likely to involve activation of pathways independent of nuclear actions of CTNNB1.

Surface components of sperm isolated from the cauda epididymides were stabilized by whole sperm fixation for immunization of rabbits. The resulting immunoglobulins (Igs) recognized a single protein of 130 kDa (non-reduced) or 54–57 kDa (reduced) on western blots of cauda sperm. Igs recognized the same 54–57 kDa protein band on whole tissue blots of the corpus and cauda epididymidis and vas deferens. No immunoreactive bands were detected on blots of the prostate, seminal vesicles, testes, caput epididymis, or any of various non-reproductive tissues. Removal of sperm from the vas deferens prior to blotting eliminated the detection of the sperm antigen. Antibodies raised to synthetic peptides, identical in amino acid sequence to two unique spans of DEFB22, recognized the same 130/54–57 kDa antigen on western blots of both caudal sperm and the purified antigen isolated with the anti-sperm Ig. From indirect immunofluorescence, both the anti-sperm and anti-peptide Igs appeared to localize to the entire sperm surface, a pattern confirmed at the ultrastructural level. Real-time PCR identified the corpus epididymides as the major site of expression of DEFB22, with negligible expression in the testes, caput epididymides, and vas deferens. Immunostaining of epididymal sections showed DEFB22 being released into the lumen at the distal caput/proximal corpus, with sperm becoming intensely coated with DEFB22 as they reached the distal corpus. Most uterine sperm recovered from mice 4 h following copulation exhibited DEFB22 coating the entire sperm surface. By contrast, some sperm recovered from the oviduct and cumulus extracellular matrix showed loss of DEFB22 from the sperm head.

Mammalian reproductive physiology and the development of viviparity co-evolved with inflammation and immunity over millennia. Many inflammatory mediators contribute to paracrine and endocrine signalling, and the maintenance of tissue homeostasis in the female reproductive tract. However, inflammation is also a feature of microbial infections of the reproductive tract. Bacteria and viruses commonly cause endometritis, perturb ovarian follicle development and suppress the endocrine activity of the hypothalamus and pituitary in cattle. Innate immunity is an evolutionary ancient system that orchestrates host cell inflammatory responses aimed at eliminating pathogens and repairing damaged tissue. Pattern recognition receptors on host cells bind pathogen-associated molecular patterns and damage-associated molecular patterns, leading to the activation of intracellular MAPK and NFκB signalling pathways and the release of inflammatory mediators. Inflammatory mediators typically include the interleukin cytokines IL1β and IL6, chemokines such as IL8, interferons and prostaglandins. This review outlines the mechanisms of inflammation and innate immunity in the bovine female reproductive tract during health and disease condition.