Bioscientifica Proceedings

Endogenous retroviruses (ERVs) are present in the genome of all vertebrates and are remnants of ancient exogenous retroviral infections of the host germline transmitted vertically from generation to generation. Sheep betaretroviruses offer a unique model system to study the complex interaction between retroviruses and their host. The sheep genome contains 27 endogenous betaretroviruses (enJSRVs) related to the exogenous and pathogenic Jaagsiekte sheep retrovirus (JSRV), the ca...

Summary. Important improvements in the management of sows have been made over the past 20 years in Europe and the U.S.A. Nevertheless, annual productivity varied between 15 and 25 piglets weaned per sow per year in France for 1983. Reasons for such a difference in productivity have been analysed quantitatively.Marked differences exist between herds in the genotype of pig used and in the age of puberty. Transportation acts as a stress...

The pig industry is confronted with substantial losses due to piglet mortality. With 3-8% stillbirths and generally > 10% preweaning mortality, approximately one fifth of al I fetuses formed fully at the end of gestation die before weaning. Most of these losses occur in the perinatal period. Overall prenatal development (birth weight) and specific prenatal developmental and maturational processes in late gestation are predisposing factors for perinatal losses. Birth weight ...

Abstract unavailableKeywords: inhibin; oestradiol; cow; pig; FSH© 1991 Journals of Reproduction & Fertility Ltd...

Development of the corpus luteum (CL) in ruminants occurs in a rapid and time-dependent manner within 1 week after ovulation, with morphologic and biochemical changes in the cells of the theca interna and granulosa cells of the preovulatory follicle. These changes involve luteinisation of steroidogenic cells and angiogenesis to establish normal luteal function (progesterone secretion). The CL is composed of a large number of vascular endothelial cells, large and small steroido...

Abstract unavailable© Third International Symposium on Embryonic Diapause...

Summary. The processes of follicle development and puberty are closely related, and both are associated with maturation of the hypothalamic—pituitary—ovarian axis. Prenatal development of the ovary is independent of gonadotrophic stimulation. Beyond 60 days of age (postnatally), tertiary follicles develop and gonadotrophins begin to influence ovarian follicular development. Negative feedback regulation of pituitary gonadotrophins by ovarian secretions dev...

Summary. Gonadotrophins, synthesized and secreted from the basophils of the adenohypophysis, bind to various target cells and elicit a wide variety of responses. Specific receptors for gonadotrophins have been found on plasma membranes of thecal, granulosa, luteal, endometrial and myometrial cells in the female and on Leydig and Sertoli cells in the Male. Gonadotrophins exert their effects through various intracellular second messengers and control biosyn...

In vitro culture has provided new information on the mechanisms involved in fertilization where two completely different cells fuse together. At the same time, results obtained in vitro have led to new questions. Does the follicle influence the final maturation process of the oocyte and does the oviduct regulate the normal behaviour of spermatozoa? Recent studies indicate a critical influence of both the follicular compartment and the oviduct on the norm...

The formation, normal function and destruction of corpora lutea are essential features of normal reproduction. Although the formation of corpora lutea from follicles is largely dependent on pituitary gonadotrophins, the process of luteolysis is locally regulated and poorly understood. The corpus luteum consists of several steroidogenic and nonsteroidogenic cell types that interact with each other in a paracrine manner. Under cell culture conditions, large luteal cells tha...