Bioscientifica Proceedings

Summary. Concentrations of β-endorphin were quantified in peripheral blood plasma of sheep by a radioimmunoassay that cross-reacted with β-lipotrophin. Plasma concentrations of β-endorphin increased abruptly after physical confinement, bacteraemia, and electroacupuncture treatment for induction of analgesia. In these experimental situations in which plasma concentrations of β-endorphin increased, plasma concentrations of LH often decreased....

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

Keywords: pig; metabolism; hypothalamus; ovary; pituitary© 1990 Journals of Reproduction & Fertility Ltd...

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...

Sex ratios that deviate from 1:1 have been observed in response to a number of stimuli. In this review we will discuss sex ratio biasing, and the evolutionary and molecular mechanisms thought to underlie this phenomena in mammals. The role of embryo quality will be discussed in relation to sex ratio modulation and epigenetic programing of the embryo. Sex ratio skewing has been studied in many species and several factors have been proposed as influencing secondary sex rat...

Keywords: boar exposure; puberty; gilts; pheromones© 1990 Journals of Reproduction & Fertility Ltd...

Summary. Since one bull may be responsible for impregnating numerous cows, testicular function and fertility are of critical importance. Within this broad context, this review will focus on: the effects of nutrition on reproductive development; scrotal/testicular thermoregulation; breeding soundness; and sperm function/fertility. Bulls fed above-maintenance levels of energy and protein before 30 wk of age had increased luteinizing hormone pulse frequency, hast...

Summary. This paper attempts to summarize and discuss the new evidence on the effectiveness of selection for prolificacy. In recent years selection between lines, and the adoption of formal cross-breeding programmes, have led to considerable improvements at a commercial level. Within-line selection has not been tackled seriously except in a few experiments. The mainly negative results from these should not lead to the conclusion that progress is impossibl...

The ability to mature, be fertilized and finally to develop into a viable embryo is acquired gradually by the oocyte during progressive differentiation throughout folliculogenesis. This process starts with oocyte growth during the first steps of follicular development. As the oocyte is close to its final size, other modifications occur, less spectacular but at least as important in determining the resulting ability of the oocyte to accomplish its reproductive purpose (developm...

Overview. One of the most fundamental axioms of mammalian reproduction is that pregnancy requires the support of progesterone without which it cannot be established or maintained. Though this basic physiological tenet was accepted long ago, major gaps in our understanding of the physiology of both pregnancy and parturition remain which hamper our ability to solve clinically and agriculturally significant problems such as low fertility, fetal growth restriction...