Abstract. Ultimobranchial neoplasms from 5 bulls that were extracted and assayed individually contained approximately 68% as much calcitonin activity (452 * 68 MRC mU/g) as thyroid glands from control bulls (663 f 165 MRC mU/g). These results were consistent with the ultrastructural finding that thyroid neoplasms in old bulls were composed of primitive ultimobranchial cells which contained few mature secretory granules The ultimobranchial body is derived in higher vertebrates from the terminal branchial pouch in close proximity to other endocrine glands involved in the homeostatic regulation of mineral metabolism. Ultimobranchial tissue varies in postnatal location from within the pericardial transverse septum in fish, near the parathyroid glands in birds, to incorporation within the thyroid tissue in higher mammals. In cattle the ultimobranchial body becomes incorporated in the vasculo-stromal hilus of the thyroid with an ingrowth of cell cords along connective tissue stroma of the gland [19].
The calcium (CA) content of the prepartal diet has been shown to significantly influence the development of profound hypocalcemia with paresis in dairy cows near parturition. The mechanisms by which these provocative and preventative diets influence endocrine function and skeletal metabolism are uncertain. The objective of this investigation was to evaluate the effects of feeding high and low CA diets on the ultrastructure and function of parathyroid chief cells in adult cows.The effects of feeding a low CA diet (4.9 gm/day for 30 days) was investigated in 3 non-1actating Jersey cows. The serum CA decreased from 10.7 to 8.8 mg/100 ml after 30 days.
The recently characterized hormone calcitonin (thyrocalcitonin) is synthesized and secreted by parafollicular (C-) cells present in the mammalian thyroid gland. Parafollicular cells are derived embryo logical ly from primordia of neural crest origin that migrate into the ultimobranchial body during early embryonic development.A syndrome of ultimobranchial thyroid neoplasms which shares many characteristics with medullary thyroid carcinoma in man occurs frequently in populations of old bulls. The development of these tumors may be related to a prolonged excessive intake of dietary calcium. Cows raised under similar environmental conditions do not develop ultimobranchial neoplasms. Affected bulls often have extensive skeletal disease and develop tumors in other endocrine organs.
A syndrome of ultimobranchial thyroid tumors (UTT) of aged bulls shares many characteristics with medullary thyroid carcinoma in man (Black et al. Cancer 32:867-878, 1973). Multiple endocrine tumors (pheochromocytomas, pituitary adenomas) and severe skeletal disease (vertebral osteosclerosis with ankylosing spondylosis and degenerative osteoarthrosis) often are detected coincidentally in bulls with UTT. Parathyroid hyperplasia or chief cell adenomas have been reported to occur frequently in humans with familial medullary thyroid carcinoma. However, parathyroid gland activity in bulls with UTT has not been well characterized. The objectives of this investigation were: (1) to investigate the histopathologic and ultrastructural alterations in parathyroid glands of bulls with UTT compared to control bulls of the same age range without C-cell tumors, and (2) to correlate these morphologic findings in the parathyroids with changes in serum calcium, phosphorus, and immunoreactive parathyroid hormone.
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