Undernutrition of ewe lambs in utero and in early post-natal life does not affect hypothalamic-pituitary function in adulthood.

The effect of undernutrition in utero, during late gestation (from day 100), and early neonatal life on hypothalamic-pituitary function was investigated in female lambs born to ewes fed rations calculated to provide either 100% (high; H) or 70% (low; L) of the energy requirements to sustain a twin pregnancy. Following parturition in early spring, ewes and lambs were maintained on pasture with sward heights of 6 cm (H) or 4 cm (L) until week 8 of lactation and then sward heights of 5 cm (H) or 3 cm (L) until weaning at week 14. Mean lamb birth weights were 18% lower in L than H animals (P<0.05) and mean liveweights were 23% lower in the L animals (P<0.001) at weaning at 14 weeks of age. Liveweight differences were not significant at, or after, 26 weeks of age. There were no significant differences between pre-pubertal H and L animals, either before (26 weeks) or after ovariectomy (31 weeks), with respect to hypothalamic or pituitary activity, as measured by LH pulse frequency, pulse amplitude or mean plasma LH and FSH concentrations and the responses to GnRH injection as measured by LH peak amplitude, respectively. Similarly there were no differences in any of these variables in pubertal animals at 18 months of age. At 31 weeks of age, H animals had significantly lower pituitary GnRH receptor binding (P<0.01) and lower ERalpha mRNA content (P<0.05) than L lambs. There were no differences with treatment in the abundance of mRNA for LHbeta, FSHbeta or GnRH-receptor at 31 weeks of age or in pubertal animals aged 18 months, when there were no significant differences with treatment in GnRH receptor binding or ERalpha mRNA expression. It is concluded that effects on lifetime reproductive function of female sheep of undernutrition during late gestation and early neonatal life are unlikely to be expressed through permanent changes in hypothalamic-pituitary function and are therefore attributable to effects exerted directly on the ovary.

Oxytocin receptor expression in human term and preterm gestational tissues prior to and following the onset of labour.

Oxytocin receptor (OTR) mRNA expression has previously been demonstrated in human myometrium, decidua, chorion and amnion but the effect of gestational age and the onset of labour has not been determined in these individual tissues. Spatial OTR mRNA expression was examined by in situ hybridization and ligand binding was confirmed using autoradiography with the iodinated oxytocin antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-OTA). Tissue was collected at term (>37 weeks of gestation) or preterm (24-36 weeks of gestation) caesarean section and classified as labour (contractions every 5 min associated with cervical dilatation) or non-labour. OTR mRNA expression was measured as optical density units from autoradiographs. There was a highly significant (P<0.001) effect of tissue type on expression of OTR mRNA with expression greatest in myometrium, low in decidua and chorion and not detected in placenta. Similar results were obtained with the 125I-OTA-binding studies, indicating that the message was translated. Amnion had an apparently high level of both hybridization and 125I-OTA binding in some samples, but a lack of specificity prevented quantification of the signal in this tissue type. Term myometrium (labour and non-labour) had significantly higher (P<0.01) OTR mRNA expression than preterm myometrium, but there was no further increase in mRNA concentration associated with labour onset. In contrast, 125I-OTA binding in myometrium was already high at 33 weeks and did not increase further either later in pregnancy or with labour. In decidua there was no effect of gestational age or labour onset on OTR mRNA expression or 125I-OTA binding. In summary, OTR mRNA expression in the myometrium increased in late pregnancy whereas decidual expression was much lower and did not rise at term.

Effect of undernutrition of ewes from the time of mating on fetal ovarian development in mid gestation.

Ewes were fed either 150% (High, H) or 50% (Low, L) of their energy requirements for maintenance of liveweight during early gestation. Effects of maternal nutrition on fetal ovarian size, histological structure and steroidogenic capacity were studied at Day 47 and on ovarian size and structure at Day 62 of gestation. At Day 47 of gestation, there were significantly higher concentrations of oogonia in the ovaries of L fetuses than H fetuses (105.9 v. 76.9 germ cells mm(-2); s.e. 4.94; P < 0.001). The capacity of the ovaries to secrete oestradiol (pg/ovary/24 h) at Day 47 was not affected by treatment when they were incubated either with (H, 773; L, 740; s.e. 179; not significant, n.s.) or without (H, 260; L, 290; s.e. 92.7; n.s.) ovine luteinizing hormone (oLH). At Day 62 of gestation, the process of germ cell degeneration was less advanced in L than H fetal ovaries, as indicated by higher oocyte concentrations in the former (68.4 v. 48.6 germ cells mm(-2); s.e. 3.85; P < 0 01). There was a greater percentage of meiotic cells in L ovaries (76.5 v. 18.6; s.e. 5.82; P < 0.001). It is concluded that undernutrition of the ewe from the time of mating significantly retards ovarian development in fetal ovaries.