Bioscientifica Proceedings

Summary. The variety of peptides synthesized by the corpus luteum (relaxin, vasopressin, oxytocin and oxytocin-related neurophysin) and their possible intracellular effects are reviewed. After luteinization of the granulosa cells and in response to LH and FSH, the output of oxytocin is increased. In addition, insulin-like growth factor is a very potent stimulus of oxytocin secretion. Although luteal cells respond to gonadotrophins by increased production of pr...

Summary. Litters of domestic piglets show strong sibling competition. large differences among litter-mates in birth weight and rate of growth, and, in the absence of human intervention, a high mortality rate. This combination of traits suggests that pigs are using a reproductive strategy similar to that of certain bird species which produce one or more small 'spare' young whose death or survival is determined by sibling competition. Death through competit...

In pigs, transcervical infusion of seminal plasma at the onset of oestrus advances ovulation and thus improves the chance of gametes meeting during their full fertilizing competence. An animal model that allows single uterine horn infusion was used in combination with transcutaneous sonographic monitoring of ovaries. Preparative surgery involved the detachment of one uterine horn from the corpus, leaving the caudal end open to the peritoneal cavity but sealing the corpus ...

There is increasing evidence that growth factors modulate folliculogenesis. However their precise role in the processes of follicular growth, differentiation and atresia is still unknown. Growth factors belong to complex systems, including all the factors structurally and functionally related, their receptor(s) and, in most cases, binding proteins or proteoglycans. In this review, the insulin-like growth factor (IGF) system is presented as a paradigm for the study of other gro...

Abstract unavailable© 1982 The authors...

Summary. Studies have consistently demonstrated that 4-cell pig embryos can be cultured to the blastocyst stage in a simple salt solution containing bovine serum albumin (BSA). Pig embryos appear to be detrimentally affected by lower levels of lactate and pyruvate than are mouse embryos, but in general their in-vitro requirements are similar. Results from embryos cultured between the 4-cell and blastocyst stages are consistent enough to allow the use of c...

Summary. Injection of prostaglandin (PG) F-2ct or its analogues has provided a . technique to induce parturition after Day 110 of gestation in the sow. The mean interval from PG injection to parturition ranges from 24 to 28 h, but only 50-60% of the sows farrow during an 8-10 h working day, and as many as 20% of sows may begin parturition before the injection of PG or > 22 h after the injection. The duration of parturition is positively associated with...

Keywords: pigs; nutrition; reproduction; condition; strategy© 1990 Journals of Reproduction & Fertility Ltd...

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

Summary. It is proposed that the first follicular phase in the lamb is initiated when responsiveness to oestradiol inhibition of LH secretion decreases sufficiently to permit the expression of an inherent hourly LH pulse rhythm. The hourly LH pulse rhythm is believed to drive oestradiol production to levels that induce the first LH surge. This hypothesis is based upon several considerations. First, pulsatile LH secretion invariably occurs at low frequencies in...