Bioscientifica Proceedings

Although the major source of relaxin in pigs is the corpus luteum of pregnancy, there is now evidence for relaxin gene expression and translation into protein in the theca intema cells of the preovulatory follicle, the corpus luteum of the cycle and the uterus. The theca interna cells retain their ability to express the relaxin gene and protein following ovulation. During the early stages of development of the corpus luteum, the theca-derived small lutein cells are the so...

The enhanced early embryonic survival in Chinese Meishan compared with Large- White gilts may be due, in part, to differences in ovarian and endocrine function, particularly during the periovulatory period. The overall patterns of oestradiol, LH and FSH secretion were not different between Meishan and Large-White hybrid controls during this period, although circulating inhibin concentrations were higher in Meishan gilts. Thus, there appeared to be a decreased sensitivity ...

In this paper we review three intra-luteal factors and their roles in the corpus luteum (CL). Insulin-like growth factor (IGF)-I, together with its receptor and IGF-binding proteins (IGFBPs), represent an important control system in the CL. IGF-I is a product of small luteal cells and has steroidogenic (i.e. luteotrophic) actions on large luteal cells via the type I receptor, while IGFBPs (e.g. BP-2 and 3; small cells) generally inhibit IGF-Is actions. IGF-I is particula...

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...

The expression and localization of selected growth factor systems and extracellular matrix (ECM) components that may influence oocyte maturation and fertilization within the mammalian oviduct are reported. Fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) systems could be detected by use of RT–PCR, RNase protection assay (RPA) and immunohistochemistry in bovine follicles, bovine cumulus–oocyte complexes (COC) and bovine and marmoset oviduct...

Experiments were conducted to further our understanding of the cellular and molecular mechanisms that regulate luteal function in ewes. Inhibition of protein kinase A (PKA) reduced (P < 0.05) secretion of progesterone from both small and large steroidogenic luteal cells. In addition, the relative phosphorylation state of steriodogenic acute regulatory protein (StAR) was more than twice as high (P&hairsp;<&hairsp;0.05) in large vs small luteal cells. Large steroidogenic...

High numbers of lipid droplets (LDs) in mammalian eggs are stored and maintained throughout embryo development without marked signs of their utilization. It was previously demonstrated in large domestic mammals that removing lipids from the zygote does not influence post-implantation development in terms of the rate of delivered offspring. Previously studied pig and cow eggs contain considerable amounts of LDs, while mice have a very low level of ooplasmic lipids, which allows...

Summary. Within 14 h of ovulation, follicular development in gilts was skewed towards a majority of mature follicles, based on their endocrine milieu. Oocyte maturation was also skewed, with a majority of the oocytes being meiotically more developed than the rest. Similarly, the pattern of ovulation in gilts was such that 70% of the follicles ovulated during a short period of time, while most of the remaining 30% ovulated over a more protracted period. Th...

The development of new technologies that would increase the efficiency for generation of transgenic livestock and would overcome some of the problems associated with random insertion of the transgene will greatly benefit animal agriculture. A potential alternative technology to pronuclear injection for the generation of transgenic pigs involves the isolation, culture and genetic manipulation of cell lines that can be reintroduced into the embryo for participation in the f...

The resumption of ovarian follicular development during lactation and after weaning in sows is a complex process that ultimately determines rebreeding efficiency of sows. Ovarian follicular development before weaning is heterogeneous because multiple patterns of development are observed when individual sows are compared. Sows can have relatively inactive ovaries before weaning with follicles of < 2 mm in diameter. Other sows have nonovulatory follicular waves in which...