1. Milk productions and 7d dietary records were determined on twenty-seven mothers who had been breast-feeding for 1, 3, 6, 9, 12 or 15 months.2. Themeanmilk productionsforeach groupofmotherswas 1.187, 1,238, 1~128,04M4.0.880and 0.951 kg/24h at 1, 3, 6, 9, 12 and 15 months of lactation respectively. There was no significant difference between two milk determinations 3-7d apart on each mother or between the mean milk production of each group of mothers. 3. Energy intakes of the infants was found to be higher than the usually-accepted values at 1 and 3 months of age but by 6 months were similar to the accepted normal values.4. Energy intakes of the mothers although greater than those recommended for similar non-lactating women were not sufficient to take into account the energy content of the milk.

The relationship between post-natal changes in blood glucose and hepatic enzyme induction was examined in the newborn rat after delivery in the last 3 days of gestation (22 days). A period of transient hypoglycaemia followed normal birth, delivery under ether anaesthesia on day 21 and delivery without anaesthesia on day 22. When fetuses were delivered without anaesthesia on days 20 and 21 the blood glucose concentration was low at birth, was constant for 3 h then increased at a rate similar to that observed for older animals. Phosphopyruvate carboxylase and tyrosine aminotransferase developed in utero after day 21 and at term the activities were high and increased immediately after birth. The time lag for the increase in enzyme activity shortened as gestation progressed. It is concluded that postnatal changes in blood glucose concentration do not have any specific effect on hepatic enzyme induction.

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1. Adrenaline increased hepatic tyrosine aminotransferase activity when injected into foetal rats or 2-day-old rats. 2. The inhibition of the postnatal increase in tyrosine aminotransferase activity which occurred in adrenalectomized newborn rats rapidly overcome by injection of adrenaline or dibutyryl cyclic AMP. 3. The effects of adrenaline or dibutyryl cyclic AMP on the tyrosine aminotransferase activity in foetal, adrenalectomized newborn and 2-day-old rats could be partially or completely blocked by prior treatment with actinomycin D. 4. Dibutyryl cyclic AMP induced tyrosine aminotransferase activity in hepatocytes cultured from 15-day foetal rats in glucocorticoid-free medium. 5. Actinomycin D at 0.2 microgram/ml in the culture medium completely prevented the induction of tyrosine aminotransferase activity by dibutyryl cyclic AMP in cultured cells. 6. The results suggest that adrenaline and cyclic AMP stimulate a transcriptional event during induction of tyrosine aminotransferase in perinatal liver.

This report describes some hormonal changes occurring in the rat during the last 3 days of gestation and the first 6 h after surgical delivery on days 20 -22 of gestation. In the foetus, the concentration of glucagon increased 2-fold and that of insulin decreased from 4.7 to 3.5 ng/ml between days 21 and 22. Consequently the insulin/glucagon molar ratio decreased from 15.6 on day 21 to 5.9 on day 22. After delivery on days 21 and 22 of gestation plasma glucagon concentration increased 2-fold and reached a maximum at 30 min after birth. In addition, the concentration of serum insulin decreased to about 50 % of the foetal values by 30 minpostpartum. Consequently the insulin/glucagon ratio decreased to a minimum 30 min after delivery. There was no significant change in the concentration of total, that bound to corticosteroid-binding globulin and free corticosterone in the plasma nor in the concentration of liver corticosterone for 6 h after delivery on day 22 of gestation. Only free plasma corticosterone concentration increased after delivery on day 21 and peaked one hour after birth. The concentration of both pancreatic hormones and corticosterone showed a different developmental pattern after premature delivery on day 20 of gestation. Plasma glucagon increased and plasma insulin decreased for 2 h. Consequently the insulin/glucagon ratio decreased from 8.8 at birth to 2.4 at 2 h post partum. The concentration of liver corticosterone as well as total, bound and free corticosterone in the plasma increased to maximal levels within 1-2 h of delivery. The results support the proposal that the relative concentration of insulin and glucagon in the blood regulate the adenosine 3': 5'-monophosphate concentration and thus enzyme induction in the liver of the perinatal rat. However, the changes in corticosterone concentration were not consistent with the view that steroids are a primary signal for tyrosine aminotransferase induction in the newborn rat.