A note on the effect of bovine somatotrophic hormone on wool production in growing lambs

SUMMARYIn two experiments carried out on 36 crossbred growing lambs the effect of purified bovine somatotrophic hormone (STH) on wool production and some qualitative fleece characters was studied. Food intake during and after the hormonal treatment was also examined. STH, injected in a dose of 1 mg/kg of body weight in 10- or 15-day intervals to growing lambs from 2 to 100 days of age, increased fleece weight significantly. This increase was accompanied by considerably higher daily food intake both during the hormonal treatment and 15 weeks after cessation of STH injections. No significant effect of STH on qualitative fleece characters was found.

INFLUENCE OF LIVER RESECTION AND REGENERATION ON SOMATOMEDIN (SULPHATION FACTOR) ACTIVITY IN SERA FROM NORMAL AND HYPOPHYSECTOMIZED RATS

ABSTRACT Somatomedin (SM) activity has been studied in the plasma of normal and hypophysectomized rats following partial hepatectomy. In normal rats a rapid disappearance of SM-activity was observed reaching a 75 per cent decrease 4–6 hours after surgery. The remaining lobes, 30 per cent of the total livers, left after hepatectomy gained in weight and were fully restored after 5–6 days. The SM-activity in the plasma from these rats slowly returned to normal level at the same rate as restoration of the resected liver tissue. In hypophysectomized rats a 35 per cent increase in relative liver weight (weight of liver in per cent of body weight) was observed 6 days after surgery in spite of the absence of the pituitary gland. Partially hepatectomized hypophysectomized rats given a pharmacological dose of human growth hormone were found to produce 40 per cent less SM-activity than control hypophysectomized rats when injected 24 hours after surgery. Administration of cycloheximide to hypophysectomized rats before growth hormone administration totally inhibited the production of SM-activity. It is concluded that the production of somatomedin in the rat is dependent on a normal liver function and that somatotrophic hormone is not an absolute necessity in the regenerating process.

CYTOLOGICAL CHANGES IN THE MOUSE ANTERIOR PITUITARY AFTER NEONATAL THYMECTOMY: A LIGHT AND ELECTRON MICROSCOPICAL STUDY

SUMMARY A detailed light and electron microscope examination of the anterior pituitary gland of mice at different times after neonatal thymectomy was performed. Neonatal removal of the thymus resulted in a progressive increase in the number of somatotrophic hormone-producing cells showing characteristic changes represented by extremely distended cisternae of the endoplasmic reticulum and reduction in the number of hormone granules. These modifications were not observed in sham-operated controls or in neonatally splenectomized mice. The functional significance of these changes in relation to thymectomy and the significance of somatotrophic hormone for the development of the thymus and for immunological maturation is discussed. It is suggested that somatotrophic hormone and possibly other hormones determine certain specific steps of differentiation of precursor cells to immunocompetent cells and that the thymus is an endocrine target gland of somatotrophic hormone.