The fetal brain and parturition

Increasing neuron numbers in the vasopressin and oxytocin containing nucleus of the adult female pig hypothalamus

Neuron number and volume of the recently described vasopressin and oxytocin containing nucleus (VON) in the pig hypothalamus have been studied into adulthood. Following a 2.5-fold increase in both sexes around puberty, both neuron number and volume of the VON continued to increase in the female pig between 1 and 2.5 years of age. Since no such increase occurred in the male, the VON exhibits a pronounced sexual dimorphism in adulthood of 260%.

Spontaneous uterine activity and plasma progesterone and oestrogens in the ewe with live and stillborn lambs

Peripheral plasma progesterone and oestrogen concentrations were measured during late pregnancy and the parturient period in 12 ewes producing live lambs and three others producing stillborn lambs. Progesterone values started declining by 10 days before lambing but at minus 24 hours were still 6.1 +/- 3 ng/ml in the ewes bearing live lambs; during the last 24 hours progesterone was significantly lower in the ewes producing stillborn lambs. Oestrogens reached a maximum level of 550 +/- 280 pg/ml at the time of delivery and declined rapidly to basal values shortly after lambing. Oestrogens did not rise at lambing in the ewes producing stillborn lambs. In seven of the 12 ewes bearing live lambs, uterine activity, as determined by intrauterine pressure changes, was recorded throughout parturition and compared with the plasma values for progesterone and oestrogens. It was found that there was a highly significant positive correlation between uterine activity and plasma oestrogen concentrations, and a highly significant negative correlation between uterine activty and both plasma progesterone concentrations and the progesterone: oestrogen ratio.