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Biomedical subjects

I A Forsyth

Publications and source records attributed to I A Forsyth.

At least 73 records · Page 4Linked to original sources
PubMed1975

Assay of lactogenic hormones using receptors isolated from rabbit liver.

Using 125-I-labelled ovine prolactin and receptors isolated from the livers of rabbits, a sensitive method has been developed suitable for the assay of ovine, bovine, porcine, human and rat prolactins. These hormones showed competitive displacement of 125-I-ovine prolactin which was in general agreement with their respective activities in the pigeon crop sac bioassay. Human and monkey growth hormones and human placental lactogen, which have marked prolactin-like actions on mammary tissue were also effective competitors. Non-primate growth hormones (ovine, bovine, equine and canine) which do not have prolactin-like activity gave little if any displacement as did human FSH, LH, TSH, ACTH and bovine insulin. Preparations of equine and canine prolactin of varying purity gave dose-response curves although their activity as competitors relative to ovine prolactin was poor and not related to their pigeon crop stimulating activity. This indicates species differences between prolactins in hormone-receptor interaction. Experiments with antiserum to human growth hormone have suggested an effective method of making the assay specific in species such as man in which prolactin is not the sole hormone with lactogenic activity.

Animals↗
PubMed1975

Studies on mild composition and lactogenic hormones in the mare.

Small samples of mammary secretion were collected from eight Thoroughbred mares during the last week of pregnancy, at foaling and after 1 week of lactation. Specific assays showed the presence of both lactose and triglyceride in all samples before birth and progressive increases in their concentrations in colostrum and in milk. Levels of 6-0 g lactose/100 ml and 1-8 g triglyceride/100 ml were present in milk at 7 to 9 days post partum. The secretory capacity of the udder is thus normally established well before parturition in the mare. Attempts to demonstrate the occurrence of a placental lactogen and to measure lactogenic hormones in plasma have been unsuccessful.

Animals↗
PubMed1972

Interactions of insulin, corticosterone and prolactin in promoting milk-fat synthesis by mammary explants from pregnant rabbits.

1. The rate of fatty acid synthesis by mammary explants from rabbits pregnant for 16 days or from rabbits pseudopregnant for 11 days was stimulated up to 15-fold by culturing for 2-4 days with prolactin. This treatment initiated the predominant synthesis of C(8:0) and C(10:0) fatty acids, which are characteristic of rabbit milk. 2. Inclusion of insulin in the culture medium increased the rate of synthesis of these medium-chain fatty acids. By contrast the inclusion of corticosterone led to the predominant synthesis of long-chain fatty acids. When explants were cultured for 2-4 days with insulin, corticosterone and prolactin, the rate of fatty acid synthesis increased up to 42-fold, but both medium- and long-chain fatty acids were synthesized. 3. These results show that the stimulus to mammary-gland lipogenesis and the initiation of synthesis of medium-chain fatty acids observed between days 16 and 23 of pregnancy in the rabbit can be simulated in vitro by prolactin alone. 4. When mammary explants from rabbits pregnant for 23 days were cultured for 2 days with insulin, corticosterone and prolactin, the rate of fatty acid synthesis increased fivefold, but there was a preferential synthesis of long-chain fatty acids. Culture with prolactin alone had little effect on the rate or pattern of fatty acids synthesized. 5. The results are compared with findings in vivo on the control of lipogenesis in the rabbit mammary gland, and are contrasted with the known effects of hormones in vitro on the mammary gland of the mid-pregnant mouse.

Acetates↗
PubMed1971

Plasma prolactin activity in inappropriate lactation.

Using a bioassay dependent on the development of a lactogenic response in rabbit mammary tissue cultured in vitro, prolactin distinct from immunoreactive growth hormone has been found in the plasma of patients of both sexes with inappropriate lactation with and without evidence of pituitary tumours. It has also been found in one patient with primary hypothyroidism and galactorrhoea, and in another during chlorpromazine therapy, but not in nine patients with gynaecomastia without galactorrhoea. Plasma prolactin levels were examined in seven patients during oral glucose tolerance tests: no change occurred in the four patients with pituitary tumours, but the levels were suppressed in the three patients with normal pituitary fossae. Prolactin appears to be a distinct pituitary hormone in man, as in animals, and also to be aetiologically related to states of inappropriate lactation.

Acromegaly↗
PubMed1971

Amenorrhoea, galactorrhoea, and primary hypothyroidism with high circulating levels of prolactin.

A 22-year-old woman with primary hypothyroidism developed amenorrhoea and galactorrhoea during oral contraceptive therapy. Investigation showed high levels of circulating prolactin which rose in response to insulin-induced hypoglycaemia and were suppressed by an oral glucose load. After treatment with thyroxine normal periods returned, the galactorrhoea improved, and the prolactin levels fell to undetectable levels. The results of the prolactin and human growth hormone assays confirm that it is possible to distinguish between human growth hormone and human prolactin.

Adult↗