Bioscientifica Proceedings

In mammals, growing oocytes have characteristically high levels of RNA synthesis. After the initiation of meiosis, that is germinal vesicle breakdown, this RNA synthesis ceases. Although there is limited evidence for RNA synthesis by the zygote, significant amounts of RNA synthesis do not occur until a species-specific cell stage. In pigs, significant amounts of mRNA synthesis cannot be detected before the four-cell stage. There appear to be three qualitatively different ...

The inconsistency of data from experiments designed to show nutritional effects on embryonic survival is perplexing. However, a number of experimental models have provided some insight into the mechanisms that potentially mediate interactions between nutrition, metabolic state and embryonic survival. The developing ovarian follicle provides the maturational environment for the oocyte, and differences in follicular maturation are associated with differences in the ability ...

Much effort is being made to establish relationships between the molecular events that take place in spermatozoa under fertilizing conditions and actual sperm function during fertilization. During capacitation, the process that 'primes' spermatozoa for interaction with the egg, components of the sperm's environment, notably bicarbonate, provoke various specific changes in the architecture and functioning of the sperm plasma membrane in a large number of cells. The individ...

The changing global needs for food and animal products require the development of breeding strategies for maximizing genetic improvement while maintaining genetic diversity. Genetic diversity can be conserved by using separate breeding herds; however, they may be expensive to maintain and inbreeding becomes a major concern. Alternative methods are needed to preserve valuable genetic resources in a reasonable and economic manner. Embryo cryopreservation allows indefinite s...

Fertilization of the egg, or oocyte, initiates the entire developmental process, but while the mechanism by which the spermatozoa triggers the oocyte to resume meiosis has been studied extensively, conclusions about this process are still elusive. Some workers have suggested that a molecule on the surface of the spermatozoon may interact with a receptor on the plasma membrane of the oocyte, thereby triggering the oocyte to resume meiosis. Other workers have focused on a ...

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...

Great advancements in cryopreservation of pig embryos have been made since the last International Conference on Pig Reproduction (ICPR). In 1997, there were standard methods to cryopreserve germplasm and embryos of most livestock species, except for the pig, and development of this technology for use in the international pig industry was slow and in the early stages. Since 1997, there have been advancements in cryopreservation of pig embryos, with reports of production o...

In all vertebrate species studied, the main central population of GnRH neurones, which produces the final messages regulating reproduction, originates outside the brain. Early during fetal life, they appear in the olfactory placode epithelium and then migrate toward the base of the telencephalon in close association with the nervus terminalis, penetrate the brain within the nervus terminalis roots, reach their final locations and eventually grow axons toward their targets. Onl...

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...

The occurrence of puberty in the female is due to the interplay of central and peripheral mechanisms in which the hypothalamic-pituitary-ovarian axis regulates growth and gonadal function, as well as adipocyte hormone secretion. Hypothalamic GnRH mRNA expression increased at 3.5 months of age and declined by 6 months of age. Concomitant with the age related reduction in the oestrogen negative feedback on LH secretion was a decline in hypothalamic oestrogen receptor-&alph...