Bioscientifica Proceedings

As stated in the first Proceedings, the economically important domestic species have been the subject of ongoing reproductive research over many decades. The aims of researchers and clinicians have been directed at increasing fecundity and fertility, to manipulate reproduction for simpler management, to increase the genetic influence of selected individuals and importantly to improve animal welfare. A group of international researchers initiated the first symposium in Australi...

The oviduct controls the environment in which the gametes are transported and fuse, and in which embryonic development begins. The ultrastructural topography of the ampulla and isthmus is similar, consisting of ciliated and secretory cells, but a different array of proteins is secreted by each segment along with various serum components. Amino acids are selectively secreted by the oviduct; these amino acids probably interact with the gametes or embryo to facilitate the process...

Enhanced secretion of PGF2α from endometrial explants in vitro in response to oxytocin is associated with augmented activities of phospholipase A2, phospholipase C and prostaglandin endoperoxide H synthase (PGS). In early pregnancy, maintenance of the corpus luteum is associated with an absence of pulsatile PGF2α secretion; an increase in endometrial inhibitors of phospholipase A2 and PGS contribute to the antilute...

Trophoblast invasiveness in ruminants is limited to fusion of migrating binucleate cells with uterine epithelium, but considerable tissue remodelling and angiogenesis occurs within the endometrium at implantation. Such processes are elsewhere associated with an altered balance of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). ProMMPs-1, -2, -3 are secreted by cultured ovine endometrial stromal, but not epithelial, cells and expression of proMMP-1 and pro...

Implantation is a critical step in the progress of pregnancy, during which the conceptus acquires a fixed position within the uterine lumen, and leads to the establishment of the placental structures. This process implies some cellular modifications of both the uterine epithelium and the trophoblast to ensure cell adhesion between the two tissues. In ruminants, the implantation process is characterized by three main steps: a long pre-attachment period lasting 2–3 weeks d...

During luteal regression episodic pulses of oxytocin secretion become coupled to the release of prostaglandin F2α (PGF2α) following synthesis of endometrial oxytocin receptors, but in early pregnancy the inhibition of oxytocin receptor formation by the conceptus prevents the development of the pulsatile pattern of PGF2α release needed to achieve luteolysis. Oxytocin receptors are present on the luminal epithelium in ovariectomize...

Interactions of the conceptus with the immune system can involve either anti-sperm or anti-conceptus immune responses that limit the success of pregnancy or beneficial effects of cytokines released from lymphoid cells on embryonic growth and gene expression. The immune system is functional in the uterus and therefore there is the potential for anti-conceptus immune responses. However, endometrial lymphocytes are distinct in many respects from lymphoid cells at peripheral sites...

Ruminant placentae produce at least two distinct subclasses of the growth hormone/prolactin gene family, the placental lactogens and prolactin-related proteins. Placental lactogens have been purified from cattle, goat and sheep placentae, and the amino acid sequences of bovine and ovine placental lactogen are known. Bovine and ovine placental lactogens are structurally more similar to prolactin than they are to growth hormone. In addition, six unique mRNAs have been described ...

In domestic ruminants the parenchyma of the corpus luteum consists of two subpopulations of steroidogenic cells commonly referred to as small and large luteal cells. These cells differ not only in size and structural characteristics, but also in functional properties. During the mid-luteal phase of the oestrous cycle approximately 60% of the corpus luteum is occupied by steroidogenic cells. Although the steroidogenic capacity of these cells declines as pregnancy advances, ...