C.G. Scanes

Radioimmunoassay of prolactin in the plasma of the domestic fowl.

Abstract A homologous radioimmunoassay for chicken prolactin is described. Chicken pituitary prolactin reacts strongly in the assay but chicken pituitary growth hormone does not. Pituitary prolactin from sheep, and plasma from ducks and pigeons do not cross-react, but plasma from the turkey reacts well. Immunoreactive prolactin in chicken plasma is greatly elevated after administration of a salt load. Prolactin levels are high in laying hens. Gonadectomy has no significant effect on circulating prolactin levels. Immature cockerels of different ages show different mean prolactin levels, prolactin being high at 8 weeks old, when mean luteinising hormone levels are low, and low at 14 weeks old, when LH levels are high.

Growth hormone effects on in vitro metabolism of avian adipose and liver tissue.

Abstract Chicken growth hormone stimulated the rate of in vitro lipolysis in adipose tissue explants from domestic fowl, turkeys, and intact and hypophysectomised feral pigeons. This stimulation was dose related and did not require the presence of glucocorticoids. Lipogenesis in chick hepatocytes was enhanced by insulin treatment and this effect was abolished by the presence of mammalian or avian GH in the incubation medium.

Prolactin release in vitro and in vivo in the pigeon and the domestic fowl following administration of synthetic thyrotrophin-releasing factor (TRF)

Chicken and pigeon pituitaries were incubated in vitro in the presence of different concentrations of hypothalamic extract and of synthetic thyrotrophin-releasing factor (TRF). It was found that prolactin, measured by pigeon crop-sac bioassay, was released in both species. The amount of prolactin released from the chicken pituitaries was increased at the higher doses of TRF, the increase occurring at a dose which corresponded to the decrease in the biphasic TSH secretion. In the pigeon, prolactin and growth hormone release in vitro were measured by an electrophoretic-densitometric method. Both prolactin synthesis and release showed a biphasic response to the dose level of TRF, as did growth hormone synthesis. n nThyrotrophin-releasing factor administered in vivo in pigeons resulted in a significant cropsac response, which was biphasic with respect to dose of TRF. There were also corresponding changes in pituitary prolactin content.

Purification and properties of an avian prolactin

Abstract Prolactin was isolated from chicken adenohypophyses by extraction of the frozen glands with alkaline ethanol and chromatography on Sephadex G100 and DEAE-cellulose. The resulting preparation was homogeneous in disc electrophoresis on polyacrylamide gel and had strong pigeon crop sac stimulating activity. The chicken prolactin had significant mammotrophic activity in pseudopregnant rabbits. Furthermore, a radioactively labeled preparation showed binding to mammary tissue in vivo . The amino acid composition of the purified avian prolactin closely resembles that of mammalian prolactin preparations and the isoelectric point is also similar in both cases.

Ionic and endocrine factors influencing the secretion of luteinizing hormone by chicken anterior pituitary cells in vitro.

Abstract A dispersed cell incubation technique has been used to study the effects of various factors associated with calcium deficiency and steroid hormones on LH release by the chicken anterior pituitary gland. In vitro LH secretion was reduced in the presence of low medium calcium concentration and also by bovine parathyroid hormone. The inclusion of 1,25-dihydroxycholecalciferol in the incubation medium prevented the stimulation of LH release by LH releasing hormone (LHRH). These results may be of significance in relation to the loss of reproductive activity in the calcium-deficient hen. Progesterone had no effect on LH production by the incubated cells, whereas testosterone enhanced LH output and its effect could be prevented by the androgen antagonist cyproterone acetate. Oestradiol reduced LH release and prevented stimulation by LHRH.

Plasma testosterone levels in male turtles, Chrysemys picta, following single injections of mammalian, avian and teleostean gonadotropins☆

The response of male turles (Chrysemys picta) to single injections of either mammalian (human, ovine), avian (domestic hen) or teleostean (salmon) gonadotropins was studied at different points of the testicular cycle (May, July, November) by measurement of plasma testosterone. Mammalian FSHs and avian FSH and LH were markedly stimulatory, and the responses were qualitatively and quantitatively similar. Further, the condition of the testis at the time of injection did not appear to affect the response, with the exception that it was quantitatively less in May. The response was characterized by: (a) Rapidity, reaching maximum or near maximum between 1 and 2 hr postinjection. (b) Magnitude, rising from 10 to 20 ng T/100 ml plasma to 1200 ng/100 ml plasma. (c) Duration, not returning to original plasma levels of T until between 96 and 192 hr postinjection. Injections of purified ovine and human FSH at levels calculated to be equivalent in hormone content to 50 μg of ovine FSH standard duplicated the response. The response was dose related, a 50 μg dose of ovine FSH evoking a response about 10-fold that of a 5 μg injection. Injections of up to 50 μg of NIH ovine LH standard, or 25 μg purified ovine LH only doubled plasma T levels and 100 μg of teleostean gonadotropin had no effect.

Diurnal variation in plasma luteinising hormone levels in the domestic fowl (Gallus domesticus).

Abstract Variations in the concentration of luteinising hormone (LH) in the blood were measured over 24 hr in sexually immature chickens maintained on long daily photoperiods of 18L:6D, 16L:8D, or 14L:10D. A significant increase in the concentration of LH occurred shortly after the onset of the dark period in both sexes. The possible significance of this observation in relation to neural control of the ovulatory cycle is discussed.

Studies on the purification and properties of avian gonadotrophins

Abstract The gonadotrophins were extracted from chicken anterior pituitary glands and separated by CM-Cellulose chromatography. Follicle stimulating hormone (FSH) was purified by chromatography on calcium phosphate and DEAE-cellulose. Luteinizing hormone (LH) was fractionated on DEAE-cellulose. The avian gonadotrophins had amino acid compositions that closely resembled those of their mammalian counterparts.

Endocrine studies in young chickens of the Obese strain

Abstract Differences between chicks of the Obese strain and those of the parent strain have been investigated. In the Obese chicks, the bursa of Fabricius was smaller (at 1 day, 2 weeks, and 4 weeks of age) and the thyroid gland was heavier (at 2 weeks of age) than in chicks of the parent stock. The level of circulating prolactin was considerably higher in the Obese chicks (at 2 and 4 weeks) and a difference in the plasma growth hormone concentration was found in the 4-week-old birds.

In vivo effects of an antiserum to partially purified chicken luteinizing hormone (CM2) in laying hens

Abstract An injection of an antiserum raised against partially purified chicken LH (fraction CM2) in laying hens resulted in a cessation of laying for about 5 days and caused extensive atresia of the ovary. Ovulation was blocked before there were macroscopic signs of follicular atresia. Since the antiserum contained antibodies against TSH and possibly FSH, these effects may not have been entirely due to the inhibition of LH activity.