Bioscientifica Proceedings

Summary. Kisspeptin is a hypothalamic neuropeptide that is critical for fertility. In virtually all species, kisspeptin neurons stimulate gonadotrophin-releasing hormone (GnRH) secretion and act as transmitters for sex-steroid feedback to GnRH neurons. In sheep, kisspeptin neurons are located in the preoptic area and the arcuate nucleus (ARC), with the latter involved in both oestradiol positive and negative feedback regulation of GnRH. In addition, sheep are ...

Abstract unavailable© 2009 Society for Reproduction and Fertility...

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...

Summary. In cattle we have noted that the antral follicle count (AFC, follicles ≥3 mm in diameter) varies greatly among animals (from 5 to 50), is repeatable within animals, and is highly correlated with the total number of healthy follicles in ovaries. Also, animals with low AFC have higher serum concentrations of FSH and LH, but lower concentrations of Anti-Mullerian Hormone, progesterone and androgens than animals with high AFC. We have investigated t...

Transport of post-partum cows or sheep before an oestradiol-induced LH surge delayed gonadotrophin secretion possibly by affecting hypothalamic activity but not via an opioid mediated mechanism as the effect could not be reversed by naloxone. In addition, reduced LH responses to GnRH were observed in cattle during transport. In sheep, adrenocorticotrophic hormone (ACTH) also diminished the LH response to GnRH, but only when GnRH was administered 3 h after ACTH, not after 0.5 h...

Sheep are seasonal breeders and reproductive status is controlled by photoperiod. Recent recognition of the significant role for kisspeptin and gonadotropin inhibitory hormone (GnIH) in the regulation of gonadotropin releasing hormone (GnRH) cells has provided a new perspective in the seasonal regulation of reproductive activity. Virtually all kisspeptin cells express estrogen receptors and kisspeptin is a potent stimulator of GnRH secretion. Thus, kisspeptin cells provide a c...

In contrast to nuclear inheritance, cytoplasmic inheritance in mammals is derived mostly, if not exclusively, from the maternal line. Mitochondria, and their DNA molecules (mtDNA), are the genetic units of this method of inheritance. Mammalian mtDNA codes for 13 enzymes used in the mitochondrial energy-generating pathway, oxidative phosphorylation, 22 tRNAs and two rRNAs. Although all transcripts of mtDNA and their translational products remain in the mitochondria, most ...

In most organs, remodelling of tissues after morphogenesis is minimal; however, normal ovarian function depends upon cyclical remodelling of the extracellular matrix (ECM). The ECM has a profound effect on cellular functions and probably plays an important role in the processes of follicular development and atresia, ovulation, and development, maintenance and regression of corpora lutea. Matrix metalloproteinases (MMPs; collagenases, gelatinases, stromelysins and membrane-type...

Summary. The ovarian follicle is a key component for determining a female’s reproductive potential; however, the mechanisms regarding the factors that control formation of follicles are not well understood. Within a species, the number of follicles formed in the ovary can vary considerably among individuals. While we are beginning to better characterize the processes required for follicle formation, much still needs to be determined regarding the factors ...

The mechanisms regulating development of a single (dominant) follicle capable of ovulation during each follicular wave in cattle and atresia of remaining follicles (dominant follicle selection) are not well understood. FSH and IGF1 are known regulators of follicle growth and granulosa cell estradiol production during follicular waves. Recent evidence indicates cocaine and amphetamine regulated transcript (CARTPT), with intraovarian expression only in single-ovulating ...