Bioscientifica Proceedings

Considerable progress has been made in the in vitro production of pig embryos using improved methods for in vitro maturation (IVM) and fertilization (IVF). Despite the progress, polyspermic penetration remains a problem for in vitro-matured oocytes. Variation among boars, ejaculates and IVF protocols used in different laboratories appears to influence the incidence of polyspermy. Recent studies indicate that oviduct cells and their secretions p...

Pigs begin behavioural preparations for birth about 1-2 days before parturition. Prepartum sows wander to select a suitable site and then construct a maternal nest. The signal that initiates this behavioural cascade probably results from fetal maturation but is unknown. However, endogenous PGF2a appears to be involved early on in an endocrine pathway that projects to the brain and can generate most of the prepartum behavioural components. This period of intense activity ...

There is still much we do not understand about the metabolic requirements of oocytes and embryos. Their remarkable metabolic plasticity during in vitro culture has hampered our ability to make significant advances in culture media design that would better support optimal physiology. A new tool, metabolomics, may revolutionize what we know about the interactions between embryos and their culture environment. Armed with this knowledge, we may design more effective culture ...

Early follicular growth refers to the development of an ovarian follicle from the primordial to early antral phase. In sheep and cows these phases of growth can be classified by the configuration of granulosal cells in the largest cross–section of the follicle as types 1 (primordial), la (transitory) 2 (primary), 3 and 4 (preantral) and 5 (early antral). Follicles classified as type 1 may be highly variable within each species with respect to number of granulosal cells an...

The formation, normal function and destruction of corpora lutea are essential features of normal reproduction. Although the formation of corpora lutea from follicles is largely dependent on pituitary gonadotrophins, the process of luteolysis is locally regulated and poorly understood. The corpus luteum consists of several steroidogenic and nonsteroidogenic cell types that interact with each other in a paracrine manner. Under cell culture conditions, large luteal cells tha...

Summary. The ovarian follicle is a key component for determining a female’s reproductive potential; however, the mechanisms regarding the factors that control formation of follicles are not well understood. Within a species, the number of follicles formed in the ovary can vary considerably among individuals. While we are beginning to better characterize the processes required for follicle formation, much still needs to be determined regarding the factors ...

Keywords: prolactin; ovarian function; luteal cells; steroidogenesis; pig© 1990 Journals of Reproduction & Fertility Ltd...

Abstract unavailable© 1987 Journals of Reproduction & Fertility Ltd...

Summary. Changes in uterine blood flow throughout pregnancy appear to be due to steroid-induced alterations in uterine arterial tone and contractility. Arterial contractility is a transient reduction in luminal diameter in response to nerve stimulation or to an alpha-1 adrenergic agonist, leading to short-term reduction in uterine blood flow. Tone is the pressure exerted by an arterial segment against an intraluminal flow (distensibility) and is considere...

Summary. Several manipulation techniques including nuclear injections, nuclear transplantation, embryo splitting, chimaera production and sperm injection are discussed with special reference to their application in the pig. The nuclear injection technique is likely to be of greatest use for gene transfer. Gene transfer is feasible for pig embryos. but it is very inefficient. Efficiencies of various steps in the successful production of transgenic offsprin...