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Title: The influence of maternal nutrition during pregnancy on the pre- and postnatal development of the reproductive axis in male and female sheep
Author: da Silva, P. N. A. P.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2000
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The purpose of this thesis is to determine: 1) the consequences of nutritionally-mediated placental growth restriction on foetal growth, pituitary gonadotrophin gene expression and gonadal development at Days 77, 104 and 128 of gestation; 2) the effect of prenatal growth restriction on the subsequent onset of puberty in female and male lambs. Embryo transfer (ET) was used to achieve singleton pregnancies in peripubertal adolescent sheep. Immediately after ET, ewes were offered either a high (H, 2-2.5 x maintenance) or moderate (M, 1.25 x maintenance) level of nutrient intake until slaughter at Days 77, 104 and 128 of gestation or until delivery at term (~Day 145). High maternal intakes resulted in restricted placental mass at all gestational stages (p<0.05 to p<0.00l) and were associated with a reduction in foetal size during late gestation (p<0.0l) and at term (p<0.001). In the male foetus, pituitary gene expression for LHß, FSHß, GnRH-receptor and oestrogen-receptor, and testicular development were not perturbed by maternal overnutrition until late gestation when growth of the male foetus per se was reduced and gonadotrophin-dependent mechanisms appeared to regulate testicular development. Female foetuses from H dams exhibited fewer primordial and primary follicles at Days 104 (p<0.05) and 128 of gestation. Pituitary LHß expression was affected by overnutrition of the dams only at Day 128 of gestation (p<0. 05). It is concluded that maternal overnutrition probably had an adverse effect on ovarian development via gonadotrophin-independent mechanisms during the first two thirds of pregnancy. Prenatal growth restriction retarded the endocrine and physical onset of puberty in male lambs. The pre-pubertal rise in peripheral testosterone concentrations was delayed (p<0.01), peak testosterone concentrations were reduced (p<0.05) and testicular volume was lower (p<0.0l) in male lambs born to H compared to M dams. In contrast, the capacity of nutritionally growth-restricted female lambs to respond to natural photoperiod and to begin cyclical ovarian activity, as determined by measurement of plasma progesterone concentrations, was similar to normal birthweight ewe lambs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available