Effects of Electrocoagulation of the Foetal Lamb Hypophysis on Growth and Development

Abstract

Electrocoagulation lesions involving 70\p=n-\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.

Quantitative Development of Adipose Tissue in Foetal Sheep

“…In the nutrition series some ewes were fed, from the 90th day of pregnancy, on large amounts of a high-energy diet while the other ewes were fed restricted amounts of the medium-energy diet; the foetuses were collected when 123-127 or 146-148 days old. In the hypophysectomy series foetuses were collected when 148-150 or 164-166 days old, the removal of the pituitary between days 95 and 115 having prevented parturition in accordance with the findings of Liggins and Kennedy (1968).…”

“…It is the substrate used by brown adipose tissue for non-shivering thermogenesis (Alexander and Williams 1968;Smith and Horwitz 1969), and it is the major source of energy in unsuckled lambs (Alexander 1962). Much of-the lipid reserve in newborn lambs lies in the adipose tissue, but normal lambs of various breeds (Merino, Corriedale, Border Leicester, Dorset Horn, Border Leicester x Merino) possess little or no subcutaneous fat (Alexander and Bell 1975)in contrast to hypophysectomized foetuses which possess substantial subcutaneous depots (Liggins and Kennedy 1968). In normal lambs almost all of the adipose tissue, amounting to about 1· 5% of body weight, is of the brown variety (Gemmell et ale 1972;Alexander and Bell 1975).…”

Ovine chorionic somatomammotropin and foetal growth

“…In the sheep, only a slightly delayed growth is observed after foetal hypophysectomy (Liggins and Kennedy, 1968). The weight of ruminant foetuses increases up to day 50 of gestation, i.e.…”

Growth as affected by general hormonal factors and hormonal balances, and the limitations of such studies

“…During fetal life, hypophysectomy does not cause an arrest of growth in the rabbit (Jost, 1947) or the sheep (Liggins and Kennedy, 1968 ;Barnes et a/., 1976). After birth, pituitary regulation of ponderal growth in the rabbit only reaches its full efficiency from about 100 days onwards (Vezinhet, 1968b).…”