Bioscientifica Proceedings

The extensive use of embryo technologies has emphasized the need for assessing embryo quality by morphological techniques, such as transmission electron microscopy, immunocytochemistry for confocal laser scanning microscopy and fluorescence in situ hybridization. By a combination of these techniques, it has been possible to demonstrate: (i) that rRNA gene activation, as monitored by embryonic nucleolar development, is comparable in bovine embryos developed in vivo...

Evidence is presented that bovine somatotrophin (bST) treatment of lactating dairy cows enhances both expression of oviductal insulin-like growth factor II (IGF-II) mRNA and endometrial insulin-like growth factor binding protein 3 (IGFBP-3) mRNA between day 3 and day 7 of the oestrous cycle. mRNA encoding growth hormone (GH) receptor in endometrial tissues increased between day 3 and day 7 of the oestrous cycle. The changes induced by bST treatment may contribute to stimulatio...

The complexity of implantation necessitates intimate dialogue between conceptus and maternal cells, and precise coordination of maternal and conceptus signalling events. Maternal and conceptus-derived steroid hormones, growth factors and cytokines, as well as integrins and their ligands, have important and inter-related roles in mediating adhesion between apical aspects of conceptus trophectoderm and maternal uterine luminal epithelium that leads to formation of an epithelioch...

Polyspermic fertilization is still a major issue in porcine IVF systems. New information is available to characterize the zona pellucida (ZP) at different developmental stages by scanning electron microscopy (SEM) and by confocal microscopy to show the distribution of ZP glycoproteins. SEM images indicated no differences between in vivo and in vitro matured oocytes; however a change in the surface structure between immature and matured oocytes, as well as between mature ...

Summary. Kisspeptin is a hypothalamic neuropeptide that is critical for fertility. In virtually all species, kisspeptin neurons stimulate gonadotrophin-releasing hormone (GnRH) secretion and act as transmitters for sex-steroid feedback to GnRH neurons. In sheep, kisspeptin neurons are located in the preoptic area and the arcuate nucleus (ARC), with the latter involved in both oestradiol positive and negative feedback regulation of GnRH. In addition, sheep are ...

In this review the concept that the origins of embryonic failure occur during oocyte development is explored. The four factors that determine oocyte viability, namely a normal growth phase, adequate follicle cell support during maturation, the completion of intracellular reprogramming before fertilization and the functioning of oocyte surveillance mechanisms, form the four sections of this review. The viability of pig oocytes at the end of the growth phase is compromised...

Keywords: hypothalamus; gonadotrophin; prolactin; pig; neurocndocrine© 1990 Journals of Reproduction & Fertility Ltd...

Over the past 30 years, basic and applied studies on classical and advanced embryo technologies have generated a vast literature on factors regulating oocyte and embryo development and quality. In addition, over this period, commercial bovine embryo transfer has become a large international business. It is well recognised that bovine embryos derived in vivo are of superior quality to those derived from in vitro maturation, fertilization and culture. Relatively little has chang...

Poor reproductive efficiency is a worldwide problem affecting the dairy industry. There is substantial evidence for an association between high milk production and lower conception rates observed in cows compared to heifers. However, whether the decline in fertility is due directly to the level of milk production or other factors associated with lactation is unclear. There are various checkpoints along the developmental axis which could, in part, contribute to reduced fertilit...

Embryonic diapause is a key strategy to extend pregnancy until conditions are ideal for birth and postnatal survival. There is still a lot to discover about this unique phenomenon observed in more than 130 mammalian species. The present review aims at complementing existing research efforts by (1) identifying new directions for a better understanding of embryonic diapause in mammals and (2) considering this complex mechanism as a source of inspiration for other areas in cellul...