R. S. Comline

The composition of foetal and maternal blood during parturition in the ewe

1. Changes in the composition of foetal and maternal blood have been followed during the last 5–10 days of gestation and throughout parturition in the conscious sheep.

The development of the adrenal medulla of the foetal and new-born calf

1. The output of adrenaline and noradrenaline from the adrenal medulla during asphyxia, stimulation of the splanchnic nerves or the intra‐arterial injection of acetylcholine, has been investigated in foetal and new‐born calves up to 3 weeks of age.

Daily changes in foetal and maternal blood of conscious pregnant ewes, with catheters in umbilical and uterine vessels

1. Blood gas tensions, pH, packed cell volume (PCV) and the levels of glucose, fructose and lactic acid have been followed in foetal and maternal blood for periods of 3‐30 days in conscious ewes between 80 days gestation and term (∼ 147 days).

PO2, PCO2 and pH levels in the umbilical and uterine blood of the mare and ewe

1. Foetal and maternal blood gas tensions and pH levels have been investigated in the mare and the ewe during late pregnancy under a number of experimental conditions.

The effects of bilateral adrenalectomy or hypophysectomy of the foetal lamb in utero.

1. Foetal hypophysectomy or bilateral adrenalectomy, carried out in utero at about 100 or 125 days gestation respectively, increased the length of gestation in sheep. It was confirmed that pregnancy was not prolonged significantly if hypophysectomy or adrenalectomy was carried out on one of a pair of twins. The hypophysectomized foetus was, however, smaller and the adrenalectomized foetus larger, than the unoperated twin. 2. In about half of the previously operated foetuses intravascular catheters were inserted into both mother and foetus, either at about 125 days, for a comparison with normal catheterized foetuses, or during the post‐mature period. Both adrenalectomized and hypophysectomized foetuses appeared to have little resistance to stress or infection and the majority survived only 1‐2 weeks after the insertion of catheters. 3. Maternal peripheral plasma oestrogen, progesterone and corticosteroid concentrations did not appear to be altered by either foetal hypophysectomy or adrenalectomy and were maintained in the normal range during prolonged gestation. 4. Foetal plasma oestrogen concentrations were significantly lower after hypophysectomy or adrenalectomy than values found in control lambs. Plasma progesterone values were low in all three groups of foetuses. 5. Plasma corticosteroid concentrations after foetal hypophysectomy (12‐6 ng/ml.) or adrenalectomy (14‐7 ng/ml.) were in the same range as the values for control lambs before the pre‐partum rise (14‐6 ng/ml.). However, there was a small but significant maternal‐to‐foetal plasma corticosteroid gradient in the two operated groups whereas this difference was not found in the control animals. 6. Tissue glycogen concentrations were measured in non‐catheterized adrenalectomized and hypophysectomized foetuses. In these two groups, whether examined before 149 days or after prolonged gestation, liver glycogen concentrations were 30‐40% of those in non‐catheterized control foetuses at term. In other respects there was little apparent difference between adrenalectomized and control foetuses. 7. Hypophysectomized foetuses had significantly higher glycogen concentrations in heart, skeletal muscle and lung compared with control or adrenalectomized lambs. Plasma glucose and fructose values were also low in this group compared with control foetuses.

A comparative study of blood gas tensions, oxygen affinity and red cell 2,3 DPG concentrations in foetal and maternal blood in the mare, cow and sow

1. Blood gas tensions, pH, PCV, O2 affinity and red cell 2,3‐diphosphoglycerate (DPG) levels have been measured in uterine and umbilical blood in conscious cows and mares with indwelling vascular catheters and in sows under sodium pentobarbitone anaesthesia.

Catecholamine secretion by the adrenal medulla of the foetal and new-born foal.

1. The content and output of adrenaline and noradrenaline from the equine adrenal medulla has been investigated under different conditions in foetuses, foals and adult mares.

Fetal and Placental O2 Consumption and the Uptake of Different Metabolites in the Ruminant and Horse during Late Gestation

The use of conscious pregnant animals with indwelling catheters in both fetal and maternal circulations has enabled a variety of measurements to be made on a long-term basis. In the sheep, changes in uterine and umbilical blood flows have been followed during the latter part of gestation (for references see Comline & Silver 1974) and such measurements coupled with analyses of arterio-venous differences in oxygen and other metabolites allow the calculation of fetal and utero-placental oxygen consumption and metabolite uptake (Battaglia & Meschia 1973). The picture which has emerged is that the rates of both uterine and umbilical blood flow keep pace with the growth of the fetus so that its oxygen uptake per unit weight remains relatively constant. However, in their calculations of the energy balance of the sheep fetus Battaglia & Meschia (1973) noticed that the amount of oxygen used by the fetus was greater than could be explained by the uptake and metabolism of glucose, amino acids and other possible metabolic fuels; at least 20–25% of the total oxygen consumption remained unaccounted for.

Uterine Activity following Intravenous Administration of Oxytocin to the Foetal Sheep

CONCENTRATIONS of oxytocin in umbilical cord blood are high in the newborn human1 and in several species the foetal pituitary contains large amounts of oxytocin and neural lobe hormone carrier proteins, the neurophysins2,3. If the foetal posterior pituitary is to play a part in labour, however, it must not only secrete oxytocin but this oxytocin must pass from the foetal vasculature to the myometrial cell. No observations have been reported regarding the ability of oxytocin to produce uterine contractions when administered from the foetal side of the placenta.

The effects of bradykinin, angiotensin and acetylcholine on the bovine adrenal medulla

1. The response of the adrenal medulla to the intra‐arterial injection of angiotensin, bradykinin and acetylcholine and to splanchnic nerve stimulation has been investigated in day‐old and 3‐ to 18‐month‐old calves and in adult cats.