Bioscientifica Proceedings

Summary. Behaviour in pigs is sexually dimorphic as early as 1 month of age; mounting of penmates is observed more frequently for males than for females. This mounting reaches its highest frequency during the 2nd month of life and then declines to a low frequency in prepubertal pigs. During the prepubertal period (3-5 months of age), bipotentiality of sexual behaviour is apparent in boars because they will not only mount oestrous females but they are also...

Currently, there is no method to diagnose pregnancy non-invasively in most wildlife species that experience delayed implantation and pseudopregnancy, either during embryonic diapause or placental pregnancy. The aim of this study was to utilize farm-raised mink (Neovison vison) as a model species to evaluate changes in the fecal proteome associated with pregnancy. Specific objectives were to: 1) determine if fecal peptides were differentially abundant in parturient ver...

Summary. Seasonal variations of reproductive ability have been demonstrated in male and female sheep and goats. For the female, there is a distinct breeding season. Whilst there are large breed differences in the duration of the sexual season, oestrous cycles generally start when daylength is decreasing and end when daylength is increasing. In some breeds, ovulation without oestrus occurs during the non-breeding season. Although males are able to mate all the ...

Summary. Prolactin and LH are required for the maintenance of normal luteal structures during early pregnancy in the ewe, whilst luteolysis, induced by prostaglandin F-2α is inhibited by the presence of the conceptus. The trophoblast also secretes a local anti-luteolytic factor, trophoblastin, which is most probably a protein because it is thermolabile and inactivated by pronase. It is soluble at pH 9.6 and can be separated on Ultrogel. Trophoblastin is p...

The hypothalamo–pituitary–gonadotrophic axis develops in the sheep fetus from midgestation to late gestation. The GnRH neuronal centres seem to be fully developed in the fetus and their localization complies with the adult pattern. Pituitary gonadotrophs are responsive to exogenous GnRH and release LH and FSH in a pulsatile fashion; the highest concentrations in plasma are found during late gestation. In sheep, maturational changes of this axis continue through to ...

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...

Light microscopic semen evaluation provides useful information about a given sperm sample, but due to its subjective nature has limited prognostic value for the reproductive performance of males or the outcome of assisted fertilization. Cryptic sperm abnormalities (occurring at the molecular level) are not easily detectable by light microscopy, but can be revealed by an array of biomarkers. The latter include fluorescent markers of acrosomal status, fluorochromes detecting alt...

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...

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...