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Reproduction in Domestic Ruminants III

Reproduction in Domestic Ruminants III

Development of the Reproductive Axis

bp0003rdr9 | Development of the Reproductive Axis | REDR1994

The search for the Booroola (FecB) mutation

Montgomery GW , Penty JM , Lord EA , Broom MF

Sheep derived from the Booroola Merino strain carry an autosomal mutation (FecB) that increases ovulation rate and litter size. One approach to characterize the genetic mutation is to locate the gene using positional cloning. The locus has been mapped to a region between genes for secreted phosphoprotein 1 (SPP1) and epidermal growth factor (EGF) on sheep chromosome 6. Analysis of possible candidate genes have excluded a number of genes associated with control of repr...

bp0003rdr10 | Development of the Reproductive Axis | REDR1994

Development of the sheep ovary during fetal and early neonatal life and the effect of fecundity genes

McNatty KP , Smith P , Hudson NL , Heath DA , Tisdall DJ , O W-S , Braw-Tal R

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...

bp0003rdr11 | Development of the Reproductive Axis | REDR1994

Melatonin and the development of circadian and seasonal rhythmicity

McMillen IC , Houghton DC , Young IR

We have investigated whether the maternal melatonin rhythm provides the fetus with either a circadian or seasonal ‘signal’ during development. Our findings provide evidence that melatonin can generate and entrain the early evening peak in the daily rhythm of fetal breathing movements. In contrast, daily variations in maternal and fetal prolactin concentrations are present in pinealectomized ewes, are altered by changes in the time of onset of darkness, but are unal...

bp0003rdr12 | Development of the Reproductive Axis | REDR1994

Ontogeny of GnRH systems

Caldani1 M , Antoine M , Batailler M , Duittoz A

In all vertebrate species studied, the main central population of GnRH neurones, which produces the final messages regulating reproduction, originates outside the brain. Early during fetal life, they appear in the olfactory placode epithelium and then migrate toward the base of the telencephalon in close association with the nervus terminalis, penetrate the brain within the nervus terminalis roots, reach their final locations and eventually grow axons toward their targets. Onl...

bp0003rdr13 | Development of the Reproductive Axis | REDR1994

Role of GnRH in the ontogeny and regulation of the fetal hypothalamo-pituitary-gonadal axis in sheep

Brooks AN , McNeilly AS , Thomas GB

Adult reproductive ability is to a large extent determined by the appropriate development of the reproductive axis during fetal life. Studies have investigated the role of the fetal hypothalamus in the ontogeny and regulation of pituitary gonadal function during fetal development in sheep. Using immunocytochemistry, we examined the ontogeny of gonadotroph development in the pituitary of female sheep fetuses. At day 70 of gestation (term = 145 days), only immunopositive LH&...

bp0003rdr14 | Development of the Reproductive Axis | REDR1994

Inhibin and activin in embryonic and fetal development in ruminants

Jenkin G , McFarlane J , de Kretser DM

Inhibin, activin and follistatin are protein hormones with diverse physiological roles. The involvement of inhibin in the regulation of pituitary FSH production and secretion in adult males and non-pregnant females is well established. However, it is unlikely that inhibin plays a similar role in pregnancy in ruminants. Inhibin and activin molecules show a high degree of structural similarity to potent growth and differentiation factors of the transforming growth factor β ...

bp0003rdr15 | Development of the Reproductive Axis | REDR1994

Development of the gonadotrophic and somatotrophic axes of sheep

Polkowska J

The hypothalamo–pituitary–gonadotrophic axis develops in the sheep fetus from midgestation to late gestation. The GnRH neuronal centres seem to be fully developed in the fetus and their localization complies with the adult pattern. Pituitary gonadotrophs are responsive to exogenous GnRH and release LH and FSH in a pulsatile fashion; the highest concentrations in plasma are found during late gestation. In sheep, maturational changes of this axis continue through to ...