Bioscientifica Proceedings

The functions necessary for normal fertilization to occur in vivo or in vitro are examined and a rational approach to identifying the main features of a fertilizing spermatozoon are developed. It is concluded that methods for testing the quality of spermatozoa must probe the dynamic changes experienced by the spermatozoa during capacitation or under stressful incubation conditions. Recent developments in the multiva hate analysis of sperm motility data a...

Summary. Results of a detailed study involving 18 pregnant, 17 cyclic and 12 inseminated but non-pregnant Holstein heifers indicated the following. (1) Jugular plasma progesterone concentrations were higher (P < 0.05) in pregnant than in cyclic or in inseminated–non-pregnant animals from Days 10 through 18. (2) Jugular plasma progesterone concentrations of inseminated–non-pregnant animals could be related to heifers in which (a) fertiliz...

Neuropeptides and catecholamines are biologically active substances which play the roles of neurotransmitters, neuromodulators and cotransmitters in the central nervous system (CNS). These substances are known to regulate and influence a wide spectrum of functions; such as food and water intake, thermoregulation, growth and maturation, sexual behaviour, reproduction, function of the hypothalamic-hypophysial-organ axes, and many others. This large family of neuropeptides ...

Spermatozoa fulfil a single role, namely achieving syngamy by transporting the haploid genome to their counterpart gamete, the oocyte. Simple as this may seem, it is fraught with many difficulties, especially in the face of biological processes that enable females to select spermatozoa after they have mated multiply with several males. Conversely, the female reproductive tract sequesters a privileged sperm subpopulation in the oviductal isthmus for variable periods of ti...

Consistent production of large quantities of fertile semen is a primary concern of boar management programmes. Common visual tests such as motility are poor indicators of the fertilizing capacity of an ejaculate. Research studies have demonstrated that, in general, if motility is 60% or greater, there are no relationships among the percentage of motile spermatozoa, in vitro sperm penetration rates, farrowing rates and litter size. Biological and environmental fac...

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© 1982 The authors...

The early morphological events in pig placental development are summarized and related to the known data on differences in placental vascular efficiency between Meishan and US breeds. The activation and localization of a number of factors, the ligands and their receptors, such as insulin-like growth factor (IGF), transforming growth factor β (TGFβ), platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), as well as retinoids and cal...

The formation of primordial follicles to establish a reservoir of resting follicles and the gradual depletion of that reservoir to provide a succession of growing follicles are key to female fertility, but little is known about the regulation of these early stages of follicular development. This review summarizes the efforts of our laboratory to elucidate these critical processes in cattle. Primordial follicles first appear in fetal ovaries around the end of the first trimeste...

Summary. Exposure of male and female pigs to elevated ambient temperatures can result in reduced reproductive efficiency. When boars and gilts are exposed to heat stress, respiratory rates increase to enhance evaporative cooling because minimal sweating occurs.During early pregnancy, gilts are especially susceptible to heat stress. Decreased conception rates and reduced litter size occur when gilts are exposed to elevated ambient te...