Bioscientifica Proceedings

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...

The development of antral follicles in sheep and cattle is dependent on FSH, but large antral follicles can shift their gonadotrophic dependence from FSH to LH. The mechanisms that result in the selection of at least one ovulatory follicle from identical follicular cohorts, exposed to the same endocrine environment, still remain to be elucidated. The aim of this research was to extend in vitro results from the rodent to sheep and cattle and, using both in vivo</em...

In several ungulate species, the preimplantation trophoblast, among various secretions, produces large amounts of antiviral activity that was identified as interferon (IFN). IFNs (types I and II) are pleiotropic cytokines, which in addition to a potent antiviral activity, exert multiple effects on cell growth and differentiation, in particular on the cells of the immune system. In ruminants, trophoblastic IFN, or trophoblast protein-1 (TF-1), was found to consist of a mul...

The resumption of ovarian follicular development during lactation and after weaning in sows is a complex process that ultimately determines rebreeding efficiency of sows. Ovarian follicular development before weaning is heterogeneous because multiple patterns of development are observed when individual sows are compared. Sows can have relatively inactive ovaries before weaning with follicles of < 2 mm in diameter. Other sows have nonovulatory follicular waves in which...

The human protamine gene cluster consists of three tightly regulated genes, protamine 1 (PRM1), protamine 2 (PRM2) and transition protein 2 (TNP2). Their products are required to repackage the paternal genome during spermiogenesis into a functional gamete. They reside within a single DNase I-sensitive domain associated with the sperm nuclear matrix, bounded by two haploid-specific Matrix Attachment Regions. The nuclear matrix is a dynamic proteinaceous network that is associat...

In the current review the main fundamental biological differences in reproductive function between Bos taurus and Bos indicus cattle are discussed. Breed differences regarding puberty, estrous cycle patterns, estrous behavior, acquisition of ovulatory capacity, ovarian structures and reproductive hormones are presented. The main physiological differences that Bos indicus cattle present relative to Bos taurus cattle include: delayed age at pu...

Summary. Maternal recognition of pregnancy in sheep, cattle and goats involves physiological mechanisms that result in protection of corpora lutea from luteolysis by modification or inhibition of uterine production of luteolytic pulses of prostaglandin (PG) F-2α. Ovine, bovine and caprine luteal cells release oxytocin in a pulsatile manner during late dioestrus. Oxytocin then binds to its endometrial receptors and initiates luteolytic pulses of PGF-2&#945...

Primary cultures of luteal cells have been used to determine both acute and chronic effects of cytokines on luteal cell function and viability. Gonadotrophin-stimulated progesterone production is inhibited by interleukin 1β (IL-1β), tumour necrosis factor a (TNF-α), or gamma-interferon (IFN-γ), the last two cytokines being more effective than IL-I. In contrast, all three cytokines are potent stimulators of prostaglandin production by these cells. The mechan...

Development in vitro is influenced by embryo density, serum, somatic cell co-culture and the production of 'embryotrophic' paracrine and autocrine factors. Research in our laboratory has focussed principally on the insulin-like growth factor (IGF) family We have demonstrated that pre-attachment bovine and ovine embryos express mRNAs encoding a number of growth factor ligand and receptor genes including all members of the IGF ligand and receptor family througho...

Intra-uterine growth retardation (IUGR), caused by maternal undernutrition or placental insufficiency, is usually associated with disproportionately large reductions in the growth of some fetal organs and tissues (thymus, liver, spleen, thyroid) and impaired cellular development of other tissues (small intestine, secondary wool follicles, skeletal muscle). Growth of other tissues, most notably brain, is relatively unimpaired. In our recent study of postnatal consequences of IU...