Bioscientifica Proceedings

The mammalian corpus luteum, which plays a central role in the reproductive process because of its production of hormones such as progesterone, is an exceptionally dynamic organ. Growth and development of the corpus luteum are extremely rapid, and even when the corpus luteum is functionally mature cellular turnover remains high. Associated with this high rate of cell turnover, the mature corpus luteum receives the greatest blood supply per unit tissue of any organ, and also ex...

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...

Inappropriate maternal nutrient intake at key developmental timepoints during ovine pregnancy has a profound influence on the outcome of pregnancy and aspects of postnatal productivity. However, the responses to alterations in maternal nutrition in adult sheep are often highly variable and inconsistent between studies. The growing adolescent sheep provides a new, robust and nutritionally sensitive paradigm with which to study the causes, consequences and reversibility of prena...

In sheep, as in other mammals, ovarian follicular growth is regulated mainly by intraovarian growth factors during early development with pituitary hormones increasingly important during the final phases to ovulation. Most follicles are present as primordial structures and these express many hundreds of genes that fulfil an array of housekeeping and signalling functions. Once growth has been initiated, at least two oocyte-derived growth factors, namely growth differentiation f...

In female sheep fetuses, the mesonephros and genital ridge can be identified at days 20 and 23 of gestation (term = 145 days), respectively. Moreover oogonia can be observed at the genital ridge from as early as day 23. Around day 55 of gestation, some germ cells enter meiosis coincident with the arrival of mesonephric-derived somatic cells (i.e. the rete ovarii). From days 75, 100, 120 and 135 of gestation, primordial (one layer of flattened granulosa cells), primary (one...

Abstract unavailable© 1995 Journals of Reproduction and Fertility Ltd...

Early follicular growth refers to the development of an ovarian follicle from the primordial to early antral phase. In sheep and cows these phases of growth can be classified by the configuration of granulosal cells in the largest cross–section of the follicle as types 1 (primordial), la (transitory) 2 (primary), 3 and 4 (preantral) and 5 (early antral). Follicles classified as type 1 may be highly variable within each species with respect to number of granulosal cells an...