Bioscientifica Proceedings

Development in vitro is influenced by embryo density, serum, somatic cell co-culture and the production of 'embryotrophic' paracrine and autocrine factors. Research in our laboratory has focussed principally on the insulin-like growth factor (IGF) family We have demonstrated that pre-attachment bovine and ovine embryos express mRNAs encoding a number of growth factor ligand and receptor genes including all members of the IGF ligand and receptor family througho...

Abstract unavailableKeywords: gene transfer; gene modification; gene expression; livestock; transgenic animal© 1991 Journals of Reproduction & Fertility Ltd...

The roles of testicular hormones in the negative feedback regulation of the secretion and actions of GnRH in male domestic ruminants are reviewed, concentrating mainly on research conducted with rams. Testicular steroids have major feedback actions directly at the hypothalamus to inhibit the secretion of GnRH, although it is apparent that, under certain circumstances, the steroids also have actions directly at the pituitary gland. Further research is necessary to delineate the...

Abstract unavailable© 1982 The authors...

Two key hypotheses emerge in the literature regarding the impact of stress on reproduction in females of any species. First, prolonged stress impairs reproduction in females. Secondly, acute stress impairs reproduction, if it occurs at a critical time during the precisely timed series of endocrine events that induce oestrus and ovulation. We reviewed studies conducted in female pigs to find support or opposition for these hypotheses in female pigs. We also considered the...

The development of nuclear transfer from tissue culture cells in livestock made it possible in principle to produce animals with subtle, directed genetic changes by in vitro modification of nuclear donor cells. In the short period since nuclear transfer was first performed, gene targeting in livestock has become a reality. Although gene targeting has immediate potential in biotechnology, it is unclear whether there are practical agricultural applications, at present. ...

Abstract unavailable© 1982 The authors...

This review attempts to integrate available data on embryo-maternal communication during maternal recognition of pregnancy and implantation in the pig. Progesterone (P4) is an essential hormone that makes the uterus receptive to accept conceptuses for implantation and subsequent placentation. As well as P4, the receptive stage of the endometrium is further primed by paracrine factors secreted by the conceptus prior to and during implantation. Oestro...

The pattern of intrauterine growth and size at birth, in particular, programmes the structure and function of tissues later in life in many species, which has important implications for the incidence of adult-onset generative diseases in human populations. In mammals, the main determinant of intrauterine growth is the placental supply of nutrients which, in turn, depends on the size, morphology, transport characteristics and endocrine function of the placenta. However, compare...

Inhibition of luteolysis and establishment of pregnancy in pigs results from oestrogen secretion by the conceptuses and requires progesterone produced by the corpus luteum (CL). An integral part of maternal recognition of pregnancy in the pig is the redirection of prostaglandin (PG) F2α,secretion from endocrine (blood) to exocrine (uterus) direction and an increase of PGE2 synthesis in both the endometrium and conceptus. Uterine and conceptus ...