Search Results

You are looking at 1 - 7 of 7 items for

  • Author: G. C. LIGGINS x
Clear All Modify Search
Full access

G. C. LIGGINS

SUMMARY

Dexamethasone caused premature delivery when infused into foetal lambs at rates of 0·06–4·0 mg./24 hr. but it had no effect when administered to pregnant ewes at the rate of 4·0 mg./24 hr. Infusions into the foetus of deoxycorticosterone or corticosterone were ineffective; mixtures of dexamethasone and deoxycorticosterone did not cause parturition more rapidly than dexamethasone alone. Thus, the ability of corticosteroids to cause premature parturition appears to depend on glucocorticoid rather than mineralocorticoid activity.

Parturition induced by dexamethasone was not delayed by administration of 100 mg. progesterone/24 hr. to the ewe or to the foetus. This suggests either that withdrawal of inhibitory effects of progesterone on the myometrium can occur independently of the progesterone concentration in peripheral plasma, or that the mechanism of parturition provoked by corticosteroids in the foetus can override any regulatory influence of progesterone on myometrial contractility.

Partial aeration of the lungs was observed in lambs born vaginally at 117–123 days of gestation after receiving dexamethasone. It is suggested that this may be the result of accelerated appearance of surfactant activity.

Full access

G. C. LIGGINS

SUMMARY

Continuous and prolonged administration of corticotrophin (ACTH) to single foetal lambs at gestational ages of 88–129 days was followed by parturition on the 4th–7th day of the infusion. At birth, the foetal adrenal glands weighed at least as much as those of normal lambs at term. Infusions of cortisol into the foetus at a rate of 50 mg./24 hr. was followed by premature parturition within 5 days. Prolonged administration of the same doses of ACTH or cortisol to pregnant ewes and of oestradiol-17β to a foetus did not cause parturition. These observations indicate that the pituitary-adrenal system of the foetus may play an active part in the initiation of parturition in the ewe.

Full access

G. C. LIGGINS and P. C. KENNEDY

SUMMARY

Electrocoagulation lesions involving 70–100% of the hypophysis of 17 foetal lambs were made at various times between 93 and 136 days of gestation. Foetal growth and development after the operation was compared with that in a group of seven control lambs comprising three intact littermates of operated foetuses and four sham-operated foetuses. Hypophysial damage was found to be associated with retardation of somatic development which was most marked when the operation was performed early in gestation. Retardation was particularly evident in epiphysial development. Hypoplasia of the adrenal cortices, the interstitial cells of the testis and the thyroid glands confirmed the assumption made by previous workers based on decapitation experiments, that the foetal hypophysis exerts a trophic influence on the development of these endocrine organs. Reduced liver glycogen content and plasma glucose levels indicated a disturbed carbohydrate metabolism. Abnormal subcutaneous fat deposition suggested disorders in fat metabolism. Delayed involution of haemopoietic tissues, hypoplasia of peripheral lymphoid tissue and reduction in the number of mast cells in the skin were also noted. Structures of ectodermal origin were relatively unaffected by hypophysial lesions. It is concluded that the hypophysis of the foetal lamb subserves many of the functions attributed to it during extrauterine life.

Full access

R. J. FAIRCLOUGH and G. C. LIGGINS

SUMMARY

Binding of cortisol to plasma proteins was studied in the foetal lamb by equilibrium dialysis at 37 °C. At 122 days of pregnancy the mean level of transcortin expressed as cortisolbinding capacity was 28 ± 6 (s.d.) ng cortisol/ml plasma. During the last 14 days of pregnancy there was a progressive increase in transcortin-binding capacity to 85 ± 14 ng cortisol/ ml plasma. A sharp increase in the concentration of both protein-bound and unbound cortisol was observed over the same period. A rise in the concentration of total cortisol from around 3 to 42 ng/ml was associated with an increase in unbound cortisol from 0·2 to a maximum of 2·1 ng/ml. The concentration of albumin-bound cortisol was approximately equal to that of unbound cortisol. The mean value for the transcortin–cortisol affinity constant was 1·15 × 108 l/mol.

It is concluded that an increase in transcortin-binding capacity is partly responsible for the prepartum increase of corticosteroid levels observed in normal foetal lambs.

Full access

G. C. Liggins, G. C. Scroop and K. G. Haughey

The changes in plasma cortisol levels in response to intravenous infusions of prostaglandin E2 (PGE2), prostacyclin and 1–24 ACTH have been studied in chronically catheterized fetal sheep during the last third of gestation.

All three drugs increased plasma cortisol levels with prostacyclin being significantly more potent than either PGE2 or 1–24 ACTH. No interaction between the steroidogenic actions of 1–24 ACTH and either PGE2 or prostacyclin could be demonstrated. The steroidogenic action of PGE2 was not significantly modified by fetal hypophysectomy.

It is concluded that neither PGE2 nor prostacyclin is likely to be involved in the enhanced adrenal responsiveness to 1–24 ACTH observed in fetal sheep in the period immediately before birth.

Full access

G. C. Liggins, J.-C. Schellenberg, F. Amato, B. Godfrey and R. F. Seamark

ABSTRACT

Total sulphoconjugated and unconjugated dehydroepiandrosterone (DHA) and total oestrone were measured in plasma of intact sheep fetuses, fetuses hypophysectomized at 104–112 days and fetuses bilaterally adrenalectomized at 98–101 days. At 120–127 days, the mean concentrations of total DHA and oestrone in intact fetuses (n = 13) were 29·7 ± 4·2 (s.e.m.) nmol/l and 14·3 ± 2·8 nmol/l respectively. At term, the values for total DHA and oestrone in hypophysectomized fetuses (n = 13) of 18·0 ± 1·9 nmol/l and 9·1 ±2·0 nmol/l were significantly (P <0·05) lower than the intact group whereas in the adrenalectomized fetuses (n = 8) total DHA (80·8±13·0 nmol/l) was higher (P < 0·05) and total oestrone values were similar to the intact animals. Intrafetal infusion of cortisol at term (1 mg/h for 84 h) raised levels of total oestrone in intact (n = 6; 12·3 ± 2·9 vs 31·6± 8·5 nmol/l) and adrenalectomized (n = 4; 14·2 ± 2·6 vs 190·6 ± 53·0 nmol/l) fetuses and of total DHA in hypophysectomized fetuses (n = 7; 16·0±1·9 vs 31·6 ± 8·5 nmol/l) while infusion of ACTH(1–24) (5 μg/h) was without significant effect in any group. It is concluded that the ovine fetal adrenal in late pregnancy makes no significant contribution either to the high circulating concentrations of DHA sulphate or to the substrates for placental oestrogen synthesis.

J. Endocr. (1985) 104, 279–283

Full access

S. Handwerger, A. J. D'Ercole, L. E. Underwood, P. Gluckman and G. C. Liggins

Serum somatomedin C concentrations in fetal sheep and pregnant ewes from days 51 to 149 of gestation were determined by specific radioimmunoassay. In the fetus (n = 61 samples) serum somatomedin C concentrations, fitted to a regression curve, increased significantly with advancing gestation from 0·44 units/ml at 51 days to 3·99 units/ml at 149 days, an increase of 806% (P < 0·001). In the pregnant ewes (n = 14 samples), serum somatomedin C did not change during gestation. The temporal relationship between the marked increase in fetal somatomedin C concentrations and the acceleration of fetal growth is consistent with the hypothesis that somatomedin is important in the stimulation of fetal growth.